#include<stdio.h>
#include<algorithm>
using namespace std;
int r, c;
int map[310][310];
int psum[310][310];
int dyn[310][310];
void process() {
int i, j, k, l, maxi;
for (i=0;i<r;i++) for (j=0;j<c;j++) {
if (i==0&&j==0) psum[i][j] = map[i][j];
else if (i==0) psum[i][j] = psum[i][j-1]+map[i][j];
else if (j==0) psum[i][j] = psum[i-1][j]+map[i][j];
else psum[i][j] = psum[i-1][j]+psum[i][j-1]-psum[i-1][j-1]+map[i][j];
}
for (i=0;i<r;i++) for (j=0;j<c;j++) {
if (i==0||j==0) dyn[i][j] = psum[i][j];
else {
maxi = 0;
for (k=0;k<i;k++) for (l=0;l<j;l++) {
maxi = max(maxi,dyn[k][l]+psum[i][j]-psum[k][j]-psum[i][l]+psum[k][l]);
}
dyn[i][j] = maxi;
}
}
printf("%d\n",dyn[r-1][c-1]);
}
void input() {
int i, j;
scanf("%d %d",&r,&c);
for (i=0;i<r;i++) {
for (j=0;j<c;j++) {
scanf("%d",&map[i][j]);
}
}
}
int main() {
input();
process();
return 0;
}
