#include <iostream>

#include <cstring>

#define maxn 5 + 2

using namespace std;

int m, n, G[maxn][maxn], dp[maxn][maxn][maxn][maxn];

int main()

{

    while (cin >> m >> n && m && n)

    {

        memset(G, , sizeof(G));

        memset(dp, , sizeof(dp));

        for (int i = ; i <= m; ++i)

            for (int j = ; j <= n; ++j)

                cin >> G[i][j];

        for (int i = ; i <= n; ++i)

            for (int j = ; j <= m; ++j)

                for (int k = ; k <= n; ++k)

                {

                    int l = i + j - k;

                    if (l >= )

                        dp[i][j][k][l] = G[i][j] + G[k][l] + max(max(dp[i - ][j][k - ][l], dp[i - ][j][k][l - ]), max(dp[i][j - ][k - ][l], dp[i][j - ][k][l - ]));

                    else continue;

                    if(i == k && j == l)

                        dp[i][j][k][l] -= G[i][j];

                }

        cout << dp[n][m][n][m] << endl;

    }

    return ;

}