#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<stack>
#include<queue>
#include<cstring>
#include<deque>
#define itn int
#define coder goodboy
using namespace std;
typedef long long LL;typedef unsigned long long ULL;
const int maxn=60;
int n,a[maxn][maxn],f[maxn][maxn][maxn][maxn],temp1,temp2,temp3,m;
inline void in(){
//	freopen("a.in","r",stdin);
	freopen("message.in","r",stdin);
	freopen("message.out","w",stdout);
	scanf("%d%d",&m,&n);
	for (int i=1;i<=m;i++){
		for (int j=1;j<=n;j++){
			scanf("%d",&a[i][j]);
		}
	}
}
inline void dp(){
	for (int i=1;i<=m;i++){
		for (int j=1;j<=n;j++){
			for (int h=1;h<=m;h++){
				for (int k=1;k<=n;k++){
					temp1=max(f[i-1][j][h-1][k],f[i][j-1][h][k-1]);
					temp2=max(f[i-1][j][h][k-1],f[i][j-1][h-1][k]);
					f[i][j][h][k]=max(temp1,temp2)+a[i][j];
					if (i!=h&&j!=k) f[i][j][h][k]+=a[h][k];
				}
			}
		}
	}
}
inline void p(){
	printf("%d",f[m][n][m][n]);
}
int Main(){
	in();
	dp();
	p();
	return 0;
}
int main(){;}
int goodboy=Main();