P13903_ca_Control_C202A.cc

#include <bits/stdc++.h>
using namespace std;

int main () {
    int n;
    cin >> n;
    for (int i=0; i < n; ++i) {
        for (int j=0; j < n; ++j) if (i%2 == j%2) cout << '.';
        else cout << '*';
        cout << endl;
    }
}