https://www.acmicpc.net/problem/23806
#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;
const int sz = 5*n;
for(int i = 1; i <= sz; i++){
for(int j = 1; j <= sz; j++){
if(i <= n || i >= sz - n + 1 || j <= n || j >= sz - n + 1) cout << "@";
else cout << ' ';
}
cout << "\n";
}
}
ㅁ을 골뱅이로 만들어 봅시다