func_code_string: #include <bits/stdc++.h>   using namespace std;   int acc[25 + 5][25 + 5];   char str[25 + 5][25 + 5];   int main() {     int N, M, ans = 0;     scanf( %d %d , &N, &M);     for (int i = 0; i < N; i++) scanf( %s , str[i]);     for (int i = 1; i < N + 1; i++)       for (int j = 1; j < M + 1; j++)         acc[i][j] = acc[i - 1][j] + acc[i][j - 1] - acc[i - 1][j - 1] +                     (str[i - 1][j - 1] ==  0  ? 1 : 0);     for (int r1 = 1; r1 < N + 1; r1++)       for (int c1 = 1; c1 < M + 1; c1++)         for (int r2 = r1; r2 < N + 1; r2++)           for (int c2 = c1; c2 < M + 1; c2++)             if (acc[r2][c2] - acc[r1 - 1][c2] - acc[r2][c1 - 1] +                     acc[r1 - 1][c1 - 1] ==                 (r2 - r1 + 1) * (c2 - c1 + 1))               ans = max(ans, 2 * ((r2 - r1 + 1) + (c2 - c1 + 1)));     printf( %d n , ans);     return 0;   }   