func_code_string: #include <bits/stdc++.h>   using namespace std;   const int mod = 1e9 + 7;   int sq[504][504], sum[504][504], dp[2][504][504];   int main() {     int n, m;     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     cin >> n >> m;     for (int i = 1; i < n + 1; ++i)       for (int j = 1; j < m + 1; ++j) cin >> sq[i][j];     for (int i = 1; i < n + 1; ++i)       for (int j = 1; j < m + 1; ++j)         sum[i][j] = sum[i - 1][j] + sum[i][j - 1] - sum[i - 1][j - 1] + sq[i][j];     int mx = -1000000000;     for (int i = 1; i < n + 1; ++i) {       for (int j = 1; j < m + 1; ++j) {         int n = i % 2, p = (i - 1) % 2,             len = min(2 * ((i - 1) / 2) + 1, 2 * ((j - 1) / 2) + 1);         dp[n][j][1] = sq[i][j];         for (int k = 3; k <= len; k += 2) {           dp[n][j][k] = sum[i][j] - sum[i - k][j] - sum[i][j - k] +                         sum[i - k][j - k] - dp[p][j - 1][k - 2] -                         sq[i - k + 2][j - k + 1];           mx = max(dp[n][j][k], mx);         }       }     }     cout << mx <<   n ;     return 0;   }   