#include <bits/stdc++.h>
using namespace std;
const int N = 51;
int n, m, f[N][N][N][N], a[N][N], x;
int main() {
    int i1, i2, j1, j2;
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++) cin >> a[i][j];

    for (i1 = 1; i1 <= n; i1++)
        for (j1 = 1; j1 <= m; j1++)
            for (i2 = 1; i2 <= n; i2++)
                for (j2 = 1; j2 <= m; j2++) {
                    int x = 0;
                    x = max(x, f[i1][j1 - 1][i2][j2 - 1]);
                    x = max(x, f[i1 - 1][j1][i2 - 1][j2]);
                    x = max(x, f[i1][j1 - 1][i2 - 1][j2]);
                    x = max(x, f[i1 - 1][j1][i2][j2 - 1]);
                    if (i1 == i2 && j1 == j2)
                        f[i1][j1][i2][j2] = x + a[i1][j1];
                    else
                        f[i1][j1][i2][j2] = x + a[i1][j1] + a[i2][j2];
                }
    cout << f[n][m][n][m];
    return 0;
}