救民于水火

#include <iostream>
#include <algorithm>

using namespace std;

int f[52][52][52][52];
int a[52][52]; 

int main()
{
    ios::sync_with_stdio(false);
    int n,m;
    int t,t2;
    cin >> m >> n;
    for (int i = 1; i <= m; ++i)
     for (int j = 1; j <= n; ++j)
      cin >> a[i][j];
    for (int i = 1; i <= m; ++i)
    {
        for (int j = 1; j <= n; ++j)
        {
            for (int k = 1; k <= m; ++k)
            {
                for (int l = 1; l <= n; ++l)
                {
                    t = max(f[i][j - 1][k - 1][l],f[i - 1][j][k][l - 1]);
                    t2 = max(f[i - 1][j][k - 1][l],f[i][j - 1][k][l - 1]);
                    f[i][j][k][l] = max(t,t2) + a[i][j] + a[k][l];
                    if (i == k && j == l)
                     f[i][j][k][l] -= a[i][j];
                }
            }
        }
    }
    cout << f[m][n][m][n] << endl;
    return 0;
}