#include <cstdio>
#include <algorithm>
using namespace std;
typedef long long ll;
int row, col;
const ll INF=9876543210000;
ll data[310][310], psum[310][310], cache[310][310];
ll get_psum(int sx, int sy, int ex, int ey)
{
ll ret = psum[ex][ey] - psum[sx-1][ey] - psum[ex][sy-1] + psum[sx-1][sy-1];
return ret;
}
ll solution(int x, int y)
{
if(x==row+1 && y==col+1) return 0;
else if(x==row+1 || y==col+1) return -INF;
ll& ret=cache[x][y];
if(ret!=-INF) return ret;
for(int i=x ; i<=row ; i++)
for(int j=y ; j<=col ; j++)
ret=max(ret, solution(i+1, j+1)+get_psum(x, y, i, j));
return ret;
}
int main(void)
{
#ifdef _CONSOLE
freopen("input.txt", "r", stdin);
#endif
scanf("%d%d", &row, &col);
for(int i=1 ; i<=row ; i++)
for(int j=1 ; j<=col ; j++)
scanf("%lld", &data[i][j]);
for(int i=0 ; i<310 ; i++)
for(int j=0 ; j<310 ; j++)
cache[i][j]=-INF;
for(int i=1 ; i<=row ; i++)
for(int j=1 ; j<=col ; j++)
psum[i][j] = psum[i-1][j] + psum[i][j-1] - psum[i-1][j-1] + data[i][j];
ll sol=solution(1, 1);
printf("%lld\n", sol);
}
