func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, i, j;     char t, w;     cin >> n;     cin >> t >> w;     bool ok = true;     if (t == w) ok = false;     for (i = 0; i < n; i++)       for (j = 0; j < n; j++) {         if (i == 0 && j < 2) continue;         char x;         cin >> x;         if ((i == j || i + j == n - 1) && x != t) ok = false;         if (!(i == j || i + j == n - 1) && x != w) ok = false;       }     if (ok)       cout <<  YES ;     else       cout <<  NO ;   }   