#include <cstdio>
#include <algorithm>
using namespace std;
int R, C;
int A[300][300], S[300][300];
int Table[300][300];
int sumA (int x1, int y1, int x2, int y2) {
return S[x2][y2] - S[x2][y1-1] - S[x1-1][y2] + S[x1-1][y1-1];
}
int main() {
scanf("%d%d", &R, &C);
for(int i = 0; i < R; i++) {
for(int j = 0; j < C; j++) {
scanf("%d", &A[i][j]);
if(i == 0 && j == 0) S[i][j] = A[i][j];
else if(i == 0) S[i][j] = S[i][j-1] + A[i][j];
else if(j == 0) S[i][j] = S[i-1][j] + A[i][j];
else S[i][j] = S[i-1][j] + S[i][j-1] - S[i-1][j-1] + A[i][j];
}
}
Table[0][0] = A[0][0];
for(int i = 1; i < R; i++) Table[i][0] = Table[i-1][0] + A[i][0];
for(int j = 1; j < C; j++) Table[0][j] = Table[0][j-1] + A[0][j];
for(int i = 1; i < R; i++) for(int j = 1; j < C; j++) Table[i][j] = sumA(0,0,i,j);
/*for(int i = 1; i < R; i++) for(int j = 1; j < C; j++) {
int v = sumA(0, 0, i, j);
for(int h = 1; h <= i; h++) {
for(int w = 1; w <= j; w++) {
v = max(v, Table[i-h][j-w] + sumA(i-h+1, j-w+1, i, j));
}
}
Table[i][j] = v;
}*/
for(int i = 1; i < R; i++) {
for(int h = 1; h <= i; h++) {
int now = (int)-2e9;
for(int j = 1; j < C; j++) {
now = max(now, Table[i-h][j-1]) + sumA(i-h+1, j, i, j);
Table[i][j] = max(Table[i][j], now);
}
}
}
printf("%d\n", Table[R-1][C-1]);
return 0;
}
