func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 502;   int n, m, l = -1, ok = 1, r;   string s[N];   int main() {     cin >> n >> m;     for (int i = 0; i < n; i++) cin >> s[i];     for (int j = 0; j < n; j++) {       l = r = -1;       for (int i = 0; i < s[j].length(); i++) {         if (l == -1 && s[j][i] ==  X )           l = r = i;         else if (l != -1 && s[j][i] ==  X ) {           r = i;         }       }       if (l != -1) break;     }     if (l == -1) {       cout <<  NO ;       return 0;     }     for (int i = 0; i < n; i++) {       int cnt = 0;       for (int j = l; j <= r; j++)         if (s[i][j] ==  X ) cnt++;       if (cnt != r - l + 1 && cnt != 0) ok = 0;     }     if (ok == 1)       for (int i = 0; i < n; i++)         for (int j = 0; j < s[i].length(); j++)           if ((j < l || j > r) && s[i][j] ==  X ) ok = 0;     if (ok)       cout <<  YES ;     else       cout <<  NO ;     return 0;   }   