func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     char mat[n][n];     for (int i = 0; i < n; i++) {       for (int j = 0; j < n; j++) {         cin >> mat[i][j];       }     }     char a = mat[0][0];     char b = mat[0][1];     if (a == b) {       cout <<  NO  << endl;       return 0;     }     for (int i = 0; i < n; i++) {       for (int j = 0; j < n; j++) {         if ((i == j || i == (n - j - 1)) && mat[i][j] != a) {           cout <<  NO  << endl;           return 0;         } else if ((!(i == j || i == (n - j - 1)) && mat[i][j] != b)) {           cout <<  NO  << endl;           return 0;         }       }     }     cout <<  YES  << endl;   }   