#include<cstdio>

#include<iostream>

#include<algorithm>

#include<cmath>

#include<cstring>

#include<string>

#include<queue>

#include<vector>

#define inf 0x3f3f3f3f

#define debug(x) cout<<"-----"<<" x = "<<x<<"-----"<<endl

using namespace std;

typedef long long ll;

const int  mod = 1e8;

const int maxn = 5e5 + ;

ll dp1[][], dp2[][], dp3[][], dp4[][];

int a[][];

int main()

{

    int n, m;

    scanf("%d%d", &n, &m);

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

    {

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

        {

            scanf("%d", &a[i][j]);

        }

    }

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

    {

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

        {

            dp1[i][j] = a[i][j] + max(dp1[i - ][j], dp1[i][j - ]);

        }

    }

    for(int i=n;i>=;i--)

    {

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

        {

            dp2[i][j] = a[i][j] + max(dp2[i + ][j], dp2[i][j - ]);

        }

    }

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

    {

        for(int j=m;j>=;j--)

        {

            dp3[i][j] = a[i][j] + max(dp3[i - ][j], dp3[i][j + ]);

        }

    }

    for(int i=n;i>=;i--)

    {

        for(int j=m;j>=;j--)

        {

            dp4[i][j] = a[i][j] + max(dp4[i + ][j], dp4[i][j + ]);

        }

    }

    ll ans = ;

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

    {

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

        {

            ans = max(ans, dp1[i - ][j] + dp4[i + ][j] + dp2[i][j - ] + dp3[i][j + ]);

            ans = max(ans, dp1[i][j - ] + dp4[i][j + ] + dp2[i + ][j] + dp3[i - ][j]);

        }

    }

    printf("%lld\n", ans);

    return ;

}