func_code_string: #include <bits/stdc++.h>   int n, m, i, j;   char s[110], p =  - ;   bool q = true;   int main() {     scanf( %d%d , &n, &m);     gets(s);     for (i = 0; i < n; i++) {       gets(s);       if (s[0] <  0  || s[0] >  9  || s[0] == p)         q = false;       else         p = s[0];       for (j = 1; j < m; j++)         if (s[j] != p) q = false;     }     if (q)       puts( YES );     else       puts( NO );     return 0;   }   