func_code_string: #include <bits/stdc++.h>   using namespace std;   namespace stuff {   void solve(int test_num) {     int R, C;     cin >> R >> C;     vector<string> grid(R);     for (int r = 0; r < R; r++) cin >> grid[r];     vector<vector<int> > cnt(R, vector<int>(C, 0));     for (int r = 0; r < R; r++) {       for (int c = 0; c < C; c++) {         const int X = grid[r][c] ==  W  ? 1 : -1;         cnt[r][c] += X;         if (r > 0) cnt[r - 1][c] -= X;         if (c > 0) cnt[r][c - 1] -= X;         if (r > 0 && c > 0) cnt[r - 1][c - 1] += X;       }     }     int res = 0;     for (int r = 0; r < R; r++)       for (int c = 0; c < C; c++)         if (cnt[r][c] != 0) res++;     cout << res << endl;   }   void solve() {     ios::sync_with_stdio(false);     cin.tie(NULL);     int T = 1;     for (int t = 1; t <= T; t++) solve(t);   }   }  // namespace stuff   int main() {     stuff::solve();     return 0;   }   