diff --git a/backend/src/endpoint/announcement.rs b/backend/src/endpoint/announcement.rs
index bdbf90af..697a65d9 100644
--- a/backend/src/endpoint/announcement.rs
+++ b/backend/src/endpoint/announcement.rs
@@ -64,7 +64,9 @@ impl AnnouncementSet for Arc<Server> {
         req: Request<ListAnnouncementRequest>,
     ) -> Result<Response<ListAnnouncementResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
@@ -82,7 +84,7 @@ impl AnnouncementSet for Arc<Server> {
             list_announcement_request::Request::Pager(old) => {
                 let pager: ColPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
@@ -101,7 +103,9 @@ impl AnnouncementSet for Arc<Server> {
         req: Request<TextSearchRequest>,
     ) -> Result<Response<ListAnnouncementResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+        
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
@@ -111,7 +115,7 @@ impl AnnouncementSet for Arc<Server> {
             text_search_request::Request::Pager(old) => {
                 let pager: TextPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
@@ -377,7 +381,8 @@ impl AnnouncementSet for Arc<Server> {
         req: Request<ListByRequest>,
     ) -> Result<Response<ListAnnouncementResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
@@ -396,7 +401,7 @@ impl AnnouncementSet for Arc<Server> {
             list_by_request::Request::Pager(old) => {
                 let pager: ParentPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
diff --git a/backend/src/endpoint/chat.rs b/backend/src/endpoint/chat.rs
index 5b316509..b9cf9d25 100644
--- a/backend/src/endpoint/chat.rs
+++ b/backend/src/endpoint/chat.rs
@@ -84,7 +84,9 @@ impl ChatSet for Arc<Server> {
         req: Request<ListByRequest>,
     ) -> Result<Response<ListChatResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+        
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
@@ -103,7 +105,7 @@ impl ChatSet for Arc<Server> {
             list_by_request::Request::Pager(old) => {
                 let pager: ParentPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
diff --git a/backend/src/endpoint/contest.rs b/backend/src/endpoint/contest.rs
index c076902e..ca0a9994 100644
--- a/backend/src/endpoint/contest.rs
+++ b/backend/src/endpoint/contest.rs
@@ -69,7 +69,9 @@ impl ContestSet for Arc<Server> {
         req: Request<ListContestRequest>,
     ) -> Result<Response<ListContestResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
@@ -87,7 +89,7 @@ impl ContestSet for Arc<Server> {
             list_contest_request::Request::Pager(old) => {
                 let pager: ColPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
@@ -103,7 +105,9 @@ impl ContestSet for Arc<Server> {
         req: Request<TextSearchRequest>,
     ) -> Result<Response<ListContestResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+        
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
@@ -113,7 +117,7 @@ impl ContestSet for Arc<Server> {
             text_search_request::Request::Pager(old) => {
                 let pager: TextPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
diff --git a/backend/src/endpoint/education.rs b/backend/src/endpoint/education.rs
index a032ae7f..1e0c6e9c 100644
--- a/backend/src/endpoint/education.rs
+++ b/backend/src/endpoint/education.rs
@@ -45,9 +45,10 @@ impl EducationSet for Arc<Server> {
         req: Request<ListEducationRequest>,
     ) -> Result<Response<ListEducationResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
-        let rev = req.reverse();
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
             list_education_request::Request::Pager(pager) => {
@@ -218,7 +219,9 @@ impl EducationSet for Arc<Server> {
         req: Request<ListByRequest>,
     ) -> Result<Response<ListEducationResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+        
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
@@ -237,7 +240,7 @@ impl EducationSet for Arc<Server> {
             list_by_request::Request::Pager(old) => {
                 let pager: ParentPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
diff --git a/backend/src/endpoint/mod.rs b/backend/src/endpoint/mod.rs
index 48e17fad..4b070191 100644
--- a/backend/src/endpoint/mod.rs
+++ b/backend/src/endpoint/mod.rs
@@ -39,4 +39,7 @@ mod tools {
     pub use tonic::*;
     pub use tracing::instrument;
     pub use uuid::Uuid;
+    pub fn split_rev(raw:i64)->(bool,u64){
+        return (raw <0,raw.abs().try_into().unwrap());
+    }
 }
diff --git a/backend/src/endpoint/problem.rs b/backend/src/endpoint/problem.rs
index a3afe640..8e1a59ef 100644
--- a/backend/src/endpoint/problem.rs
+++ b/backend/src/endpoint/problem.rs
@@ -56,7 +56,9 @@ impl ProblemSet for Arc<Server> {
         req: Request<ListProblemRequest>,
     ) -> Result<Response<ListProblemResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
@@ -74,7 +76,7 @@ impl ProblemSet for Arc<Server> {
             list_problem_request::Request::Pager(old) => {
                 let pager: ColPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
@@ -90,7 +92,9 @@ impl ProblemSet for Arc<Server> {
         req: Request<TextSearchRequest>,
     ) -> Result<Response<ListProblemResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
@@ -100,7 +104,7 @@ impl ProblemSet for Arc<Server> {
             text_search_request::Request::Pager(old) => {
                 let pager: TextPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
@@ -369,9 +373,11 @@ impl ProblemSet for Arc<Server> {
         req: Request<ListByRequest>,
     ) -> Result<Response<ListProblemResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
-        let offset = bound!(req.offset(), 1024);
 
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
+        let offset = bound!(req.offset(), 1024);
+        
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
             list_by_request::Request::Create(create) => {
                 tracing::debug!(id = create.parent_id);
@@ -388,7 +394,7 @@ impl ProblemSet for Arc<Server> {
             list_by_request::Request::Pager(old) => {
                 let pager: ParentPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
diff --git a/backend/src/endpoint/submit.rs b/backend/src/endpoint/submit.rs
index 5c47a08b..51d9d452 100644
--- a/backend/src/endpoint/submit.rs
+++ b/backend/src/endpoint/submit.rs
@@ -69,7 +69,9 @@ impl SubmitSet for Arc<Server> {
         req: Request<ListSubmitRequest>,
     ) -> Result<Response<ListSubmitResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
@@ -80,7 +82,7 @@ impl SubmitSet for Arc<Server> {
             list_submit_request::Request::Pager(old) => {
                 let pager: ColPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
@@ -97,7 +99,9 @@ impl SubmitSet for Arc<Server> {
         req: Request<ListByRequest>,
     ) -> Result<Response<ListSubmitResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
@@ -115,7 +119,7 @@ impl SubmitSet for Arc<Server> {
             list_by_request::Request::Pager(old) => {
                 let pager: ParentPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
diff --git a/backend/src/endpoint/testcase.rs b/backend/src/endpoint/testcase.rs
index 4e8d05ca..2b1c96f4 100644
--- a/backend/src/endpoint/testcase.rs
+++ b/backend/src/endpoint/testcase.rs
@@ -44,14 +44,16 @@ impl TestcaseSet for Arc<Server> {
         req: Request<ListTestcaseRequest>,
     ) -> Result<Response<ListTestcaseResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
             list_testcase_request::Request::Pager(old) => {
                 let pager: ColPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
             list_testcase_request::Request::StartFromEnd(rev) => {
@@ -250,7 +252,9 @@ impl TestcaseSet for Arc<Server> {
         req: Request<ListByRequest>,
     ) -> Result<Response<ListTestcaseResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
@@ -268,7 +272,7 @@ impl TestcaseSet for Arc<Server> {
             list_by_request::Request::Pager(old) => {
                 let pager: ParentPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
diff --git a/backend/src/endpoint/user.rs b/backend/src/endpoint/user.rs
index f455cf63..3961bd61 100644
--- a/backend/src/endpoint/user.rs
+++ b/backend/src/endpoint/user.rs
@@ -29,18 +29,6 @@ impl From<Model> for UserInfo {
     }
 }
 
-// impl From<RoleLv> for Permission {
-//     fn from(value: RoleLv) -> Self {
-//         Permission { flags: value }
-//     }
-// }
-
-// impl From<Permission> for RoleLv {
-//     fn from(value: Permission) -> Self {
-//         RoleLv(value.flags)
-//     }
-// }
-
 #[async_trait]
 impl UserSet for Arc<Server> {
     #[instrument(skip_all, level = "debug")]
@@ -49,7 +37,9 @@ impl UserSet for Arc<Server> {
         req: Request<ListUserRequest>,
     ) -> Result<Response<ListUserResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
@@ -67,7 +57,7 @@ impl UserSet for Arc<Server> {
             list_user_request::Request::Pager(old) => {
                 let pager: ColPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
@@ -83,7 +73,9 @@ impl UserSet for Arc<Server> {
         req: Request<TextSearchRequest>,
     ) -> Result<Response<ListUserResponse>, Status> {
         let (auth, req) = self.parse_request(req).await?;
-        let size = bound!(req.size, 64);
+
+        let (rev,size)=split_rev(req.size);
+        let size = bound!(size, 64);
         let offset = bound!(req.offset(), 1024);
 
         let (pager, models) = match req.request.ok_or(Error::NotInPayload("request"))? {
@@ -93,7 +85,7 @@ impl UserSet for Arc<Server> {
             text_search_request::Request::Pager(old) => {
                 let pager: TextPaginator = self.crypto.decode(old.session)?;
                 pager
-                    .fetch(&auth, size, offset, old.reverse, &self.db)
+                    .fetch(&auth, size, offset, rev, &self.db)
                     .await
             }
         }?;
diff --git a/proto/backend.proto b/proto/backend.proto
index d5c6745f..dfdf955c 100644
--- a/proto/backend.proto
+++ b/proto/backend.proto
@@ -34,7 +34,6 @@ enum MatchRule {
 // (4, 3, false) => 5, 6, 7
 message Paginator {
   required string session = 1;
-  required bool reverse = 2;
 }
 
 message TextSearchRequest {
@@ -42,7 +41,7 @@ message TextSearchRequest {
     string text = 1;
     Paginator pager = 2;
   }
-  required uint64 size = 3;
+  required int64 size = 3;
   optional uint64 offset = 4;
 }
 
@@ -55,7 +54,7 @@ message ListByRequest {
     Create create=1;
     Paginator pager = 2;
   }
-  required uint64 size = 3;
+  required int64 size = 3;
   optional uint64 offset = 4;
   optional bool reverse = 5 ;
 }
@@ -150,7 +149,7 @@ message ListSubmitRequest {
     Create create = 1;
     Paginator pager = 2;
   }
-  required uint64 size = 3;
+  required int64 size = 3;
   optional uint64 offset = 4;
   optional bool reverse = 5 ;
 }
@@ -232,7 +231,7 @@ message ListAnnouncementRequest {
     Create create = 1;
     Paginator pager = 2;
   }
-  required uint64 size = 3;
+  required int64 size = 3;
   optional uint64 offset = 4;
   optional bool reverse=5;
 }
@@ -317,7 +316,7 @@ message ListEducationRequest {
     Paginator pager =2;
   }
   optional bool reverse = 5;
-  required uint64 size = 3;
+  required int64 size = 3;
   optional uint64 offset = 4;
 }
 
@@ -417,7 +416,7 @@ message ListProblemRequest {
     Create create = 1;
     Paginator pager = 2;
   }
-  required uint64 size = 3;
+  required int64 size = 3;
   optional uint64 offset = 4;
 }
 
@@ -493,7 +492,7 @@ message ListTestcaseRequest {
     Paginator pager = 5;
   } 
   optional bool reverse = 6;
-  required uint64 size = 3;
+  required int64 size = 3;
   optional uint64 offset = 4;
 }
 
@@ -598,7 +597,7 @@ message ListContestRequest {
     Paginator pager = 2;
   }
   optional bool reverse = 6;
-  required uint64 size = 3;
+  required int64 size = 3;
   optional uint64 offset = 4;
 }
 
@@ -688,7 +687,7 @@ message ListUserRequest {
     Paginator pager = 2;
   }
   optional bool reverse = 6;
-  required uint64 size = 3;
+  required int64 size = 3;
   optional uint64 offset = 4;
 }