#include <iostream>

using namespace std;
const int N = 60;
int a[N][N];
int dp[N][N][N][N];
int main(){
	int n, m;
	cin >> n >> m;
	for(int i = 1; i <= n; i++){
		for(int j = 1; j <= m; j++){
			cin >> a[i][j];
		}
	}
	for(int i = 1; i <= n; i++){
		for(int j = 1; j <= m; j++){
			for(int x = 1; x <= n; x ++){
				for(int y = 1; y <= m; y++){
					int *t;
					t = &dp[i][j][x][y];
					*t = max(*t, dp[i-1][j][x][y-1]);
					*t = max(*t, dp[i-1][j][x-1][y]);
					*t = max(*t, dp[i][j-1][x-1][y]);
					*t = max(*t, dp[i][j-1][x][y-1]);
					*t += a[i][j] + a[x][y];
					if(i == x && j == y)
						*t -= a[x][y];
				}
			}
		}
	
	}
	cout << dp[n][m][n][m];
}