func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, m, t;     cin >> n >> m;     string s[100 + 10];     for (int i = 0; i < n; i++) {       cin >> s[i];     }     for (int i = 0; i < n; i++) {       t = s[i][0];       for (int j = 0; j < m; j++) {         if (s[i][j] != t) {           cout <<  NO  << endl;           return 0;         }       }     }     for (int i = 1; i < n - 1; i++) {       if (s[i] == s[i - 1] || s[i] == s[i + 1]) {         cout <<  NO  << endl;         return 0;       }     }     cout <<  YES  << endl;   }   