#include<stdio.h>
using namespace std;
int main()
{
freopen("flip.in","r",stdin);
freopen("flip.out","w",stdout);
int a,b,v[16][16],i,j,sum,sum1;
scanf("%i %i",&a,&b);
for(i=1;i<=a;i++)
     for(j=1;j<=b;j++)scanf("%i",&v[i][j]);
for(i=1;i<=a;i++)
    {
    sum=0;
    for(j=1;j<=b;j++)sum=sum+v[i][j];
    if(sum<0)for(j=1;j<=b;j++)v[i][j]=v[i][j]*(-1);
    }
for(i=1;i<=b;i++)
  {
  sum1=0;
    for(j=1;j<=b;j++)sum1=sum1+v[j][i];
    if(sum1<0)for(j=1;j<=a;j++)v[j][i]=v[j][i]*(-1);
    }
sum=0;
for(i=1;i<=a;i++)
  for(j=1;j<=b;j++)sum=sum+v[i][j];
printf("%i",sum);
return 0;
}