#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
int dp[300][300];
bool isVisited[300][300];
int sum[300][300];
int r, c;
int getSum(int sy, int sx, int ey, int ex)
{
int ret = sum[ey][ex];
if(sy > 0) ret -= sum[sy - 1][ex];
if(sx > 0) ret -= sum[ey][sx - 1];
if(sy > 0 and sx > 0) ret += sum[sy - 1][sx - 1];
return ret;
}
int getAns(int y, int x)
{
if(y == r and x == c) return 0;
else if(y == r or x == c) return -(1 << 29);
int &ret = dp[y][x];
if(isVisited[y][x]) return ret;
isVisited[y][x] = true;
ret = -(1 << 29);
for(int cy = y; cy < r; cy++)
for(int cx = x; cx < c; cx++)
ret = max(ret, getAns(cy + 1, cx + 1) + getSum(y, x, cy, cx));
return ret;
}
int main(void)
{
scanf("%d %d", &r, &c);
for(int i = 0; i < r; i++)
for(int j = 0; j < c; j++)
{
int &s = sum[i][j];
scanf("%d", &s);
if(i > 0) s += sum[i - 1][j];
if(j > 0) s += sum[i][j - 1];
if(i > 0 and j > 0) s -= sum[i - 1][j - 1];
}
printf("%d\n", getAns(0, 0));
return 0;
}
