# include <bits/stdc++.h>

using namespace std;
const int N=55;
int n,m,a[N][N],dp[N][N][N][N];
int main(){
	cin>>n>>m;
	for(int i = 1;i<=n;i++)
		for(int j = 1;j<=m;j++)
			cin>>a[i][j];
	memset(dp,-0x3f,sizeof(dp));
	dp[1][1][1][1]=0;
	for(int i = 1;i<=n;i++)
		for(int j = 1;j<=m;j++)
			for(int k = i+1;k<=n;k++)
				for(int l = 1;l<j;l++)
				dp[i][j][k][l]=max({dp[i-1][j][k-1][l],dp[i-1][j][k][l-1]
				,dp[i][j-1][k-1][l],dp[i][j-1][k][l-1]})+a[i][j]+a[k][l];
	cout<<dp[n-1][m][n][m-1];
	return 0;
}