#include <stdio.h>

using namespace std;

FILE* f=fopen("flip.in","r");
FILE* fout=fopen("flip.out","w");

int max1;

void back ( int a[16][16] ,int n ,int m,int c, int k ,int s)
{
        if(c<n*m)
        {if(k<n*m)
            {if(k/m!=c/m && k%m!=c%m)
            s+=a[k/m][k%m];
            else s-=a[k/m][k%m];
            }
            if(k==n*m)
            {   if(s>max1)max1=s;
                back(a,n,m,c+1,0,0);
            }
            else back(a,n,m,c,k+1,s);
        }

}

int main()
{
int n,m;
fscanf(f,"%d%d",&n,&m);
int a[16][16];
int i,j;
for(i=0;i<n;i++)
    for(j=0;j<m;j++)
    fscanf(f,"%d",&a[i][j]);
back (a,n,m,0,0,0);
fprintf(fout,"%d",max1);
    return 0;
}