#pragma warning(disable: 4786)
#pragma G++ optimize ("O2")
#pragma comment(linker, "/STACK:1024000000,1024000000")
#include <vector>
#include <cstdio>
#include <cstring>
#include <algorithm> 
#include <cctype>
#include <iostream>

#define Max(a,b) (a>b ? a:b)
#define Min(a,b) (a<b ? a:b)
#define Rep(_i,x,y) for(int _i = x; _i <= y;_i++)

using namespace std;
typedef unsigned int lg;
#define MAXX 100009

inline bool read(int &x){
	char c=getchar();
	while(c!=EOF&&!isdigit(c)) c=getchar();
	if(c==EOF) return 0; x=0;
	while(isdigit(c)) {
		x=x*10+c-'0';
		c=getchar();
	}
	return 1;
}

int a[51][51];
int f[51][51][51][51];
int n,m;

signed main(void) {
	freopen("message.in","r",stdin);
    freopen("message.out","w",stdout);
    read(n);read(m);
    Rep(i,1,n)
     Rep(j,1,m)
      read(a[i][j]);
    Rep(i,1,n) Rep(j,1,m) Rep(x,1,n) Rep(y,1,m)
	 if(i != x || j != y || (i==n&&j==m)) {
    	f[i][j][x][y] = Max (
          Max(f[i-1][j][x-1][y],f[i-1][j][x][y-1]),
          Max(f[i][j-1][x-1][y],f[i][j-1][x][y-1]) 
		) + a[i][j] + a[x][y]; 
	//cout<<i <<j<<x<<y <<f[i][j][x][y] <<endl;
	}
    cout << f[n][m][n][m];
    return 0;
}