#include <cstdio>
using namespace std;
FILE* fin= fopen("flip.in","r");
FILE*fout=fopen("flip.out","w");
int i,j,k,n,p,lmax,poz,sum;
int m[20][20];
int main()
{
    fscanf(fin,"%d%d",&n,&p);
    for (i=1;i<=n;i++)
    for (j=1;j<=p;j++)
    fscanf(fin,"%d",&m[i][j]);

if (n>=p)
{
   for (j=1;i<=p;j++)
    {
    sum=0;
    for (i=1;i<=n;i++,sum+=m[i][j]);
    if (sum<0)
    for (i=1;i<=n;i++,m[i][j]*=-1);
    }

    for (i=1;i<=n;i++)
    {
    sum=0;
    for(j=1;j<=p;j++,sum+=m[i][j]);
    if (sum<0)
    for(j=1;j<=p;j++,m[i][j]*=-1);
    }
}

if (p>n)
{
    for (i=1;i<=n;i++)
    {
    sum=0;
    for(j=1;j<=p;j++,sum+=m[i][j]);
    if (sum<0)
    for(j=1;j<=p;j++,m[i][j]*=-1);
    }

   for (j=1;i<=p;j++)
    {
    sum=0;
    for (i=1;i<=n;i++,sum+=m[i][j]);
    if (sum<0)
    for (i=1;i<=n;i++,m[i][j]*=-1);
    }
}
sum=0;
for (i=1;i<=n;i++)
for(j=1;j<=p;j++)
sum+=m[i][j];
fprintf(fout,"%d\n",sum);
    return 0;
}