#include<stdio.h>r
int R, C;
int map[301][301];
int s[301][301];
int d[301][301];
int main()
{
scanf("%d %d", &R, &C);
for(int i = 1; i <= R; i++) for(int j = 1; j <= C; j++){
scanf("%d", &map[i][j]);
}
for(int i = 1; i <= R; i++){
int t = 0;
for(int j = 1; j <= C; j++){
t += map[i][j];
s[i][j] = s[i-1][j] + t;
}
}
for(int i = 1; i <= R; i++)
{
for(int j = 1; j <= C; j++)
{
int tt = s[i][j];
for(int k = 1; k < i; k++)
{
for(int p = 1; p < j; p++)
{
int tmp = d[k][p] + (s[i][j] - s[k][j] - s[i][p] + s[k][p]);
if(tt < tmp) tt = tmp;
}
}
d[i][j] = tt;
}
}
printf("%d\n", d[R][C]);
return 0;
}
