#include <cstdio>
#include <algorithm>
#define oo 987654321
int R, C, A[311][311], S[311][311], DT[310][310];
int f(int a, int b)
{
int ans = -oo;
if( a == R+1 && b == C+1 ) return 0;
if( a == R+1 || b == C+1 ) return -oo;
if( DT[a][b] == 0 )
{
for(int i = a ; i <= R ; i++ ) for( int j = b ; j <= C ; j++ )
ans = std::max( ans, S[i][j] - S[a-1][j] - S[i][b-1] + S[a-1][b-1] + f(i+1, j+1) );
DT[a][b] = ans;
}
return DT[a][b];
}
int main()
{
scanf("%d%d",&R,&C);
for(int i = 1 ; i <= R ; i++ ) for(int j = 1 ; j <= C ; j++ )
scanf("%d", &A[i][j]);
for(int i = 1 ; i <= R ; i++ ) for(int j = 1 ; j <= C ; j++ )
if( i == 1 && j == 1 ) S[i][j] = A[i][j];
else S[i][j] = S[i-1][j] + S[i][j-1] - S[i-1][j-1] + A[i][j];
printf("%d", f(1,1));
return 0;
}
