#include<iostream>
#include<cstdio>
using namespace std;
int m,n;
int s[51][51],dp[51][51][51][51];
int main(){
	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 ",&s[i][j]);
		scanf("\n");
	}
	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++)
	if(i!=k&&j!=l||(i==1&&j==1&&k==1&&l==1)||(i==m&&j==n&&k==m&&l==n))
	dp[i][j][k][l]=max(max(dp[i-1][j][k-1][l],dp[i][j-1][k][l-1]),max(dp[i][j-1][k-1][l],dp[i-1][j][k][l-1]))+s[i][j]+s[k][l];
	printf("%d",dp[m][n][m][n]);
	fclose(stdin);
	fclose(stdout);
	return 0;
}