#include<stdio.h>
#include<algorithm>
//O(R^2 * C^2)
int d[303][303];
int p[303][303];
#define Get(a,b,c,d) (p[c][d]-p[a-1][d]-p[c][b-1]+p[a-1][b-1])
int main(){
int r,c,i,j;
scanf("%d%d",&r,&c);
for(i=1;i<=r;i++)for(j=1;j<=c;j++)scanf("%d",p[i]+j);
for(i=1;i<=r;i++)for(j=1;j<=c;j++)p[i][j] += p[i][j-1] + p[i-1][j] - p[i-1][j-1];
for(i=1;i<=r;i++)for(j=1;j<=c;j++){
int k, l;
for(k=i;k;k--)for(l=j;l;l--)
d[i][j] = std::max(d[i][j], d[k-1][l-1] + Get(k, l, i, j));
}
printf("%d",d[r][c]);
return 0;
}
