func_code_string: #include <bits/stdc++.h>   using namespace std;   bool isOk(char c, int v) { return v == (c ==  B  ? -1 : 1); }   int main() {     int n, m;     scanf( %d %d , &n, &m);     string a[n];     int v[n][m];     char ch;     int vx;     int nOp = 0;     for (int i = 0; i < n; i++) {       fill(v[i], v[i] + m, 0);       cin >> a[i];     }     for (int i = n - 1; i >= 0; i--)       for (int j = m - 1; j >= 0; j--) {         if (!isOk(a[i][j], v[i][j])) {           ++nOp;           vx = (a[i][j] ==  W  ? v[i][j] - 1 : v[i][j] + 1);           for (int i1 = 0; i1 <= i; i1++)             for (int j1 = 0; j1 <= j; j1++) v[i1][j1] -= vx;         }       }     printf( %d n , nOp);     return 0;     return 0;   }   