AtCoder abc043_a - Children and Candies (ABC Edit).cpp

//https://atcoder.jp/contests/abc043/tasks/abc043_a?lang=en
#include <iostream>
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

#define endl '\n'

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    ll n;
    cin>>n;
    cout<<(n*(n+1))/2<<endl;



    return 0;
}