https://www.acmicpc.net/problem/23802
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
#define fastio ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#define int int64_t
using namespace std;
int32_t main(){
fastio;
int n; cin >> n;
for(int i = 1; i <= 5*n; i++){
for(int j = 1; j <= 5*n; j++){
if(i <= n || j <= n) cout << "@";
}
cout << "\n";
}
}