#include<stdio.h>

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

int v[16][16],n,m;

void read()
{
 int i,j;
 fscanf(in, "%d%d", &n, &m);
 for(i=1;i<=n;i++)
  for(j=1;j<=m;j++)
   fscanf(in, "%d", &v[i][j]);
}

void secventa()
{
 int i,j,s;
 for(i=1;i<=n;i++)
  {
   s=0;
   for(j=1;j<=m;j++)
    s+=v[i][j];
   if(s<0)
    for(j=1;j<=m;j++)
     v[i][j]=v[i][j]*(-1);
  }
 for(j=1;j<=m;j++)
  {
   s=0;
   for(i=1;i<=n;i++)
    s+=v[i][j];
   if(s<0)
    for(i=1;i<=n;i++)
     v[i][j]=v[i][j]*(-1);
  }
 s=0;
 for(i=1;i<=n;i++)
  for(j=1;j<=m;j++)
   s+=v[i][j];
 fprintf(out, "%d", s);
}

int main()
{
 read();
 secventa();
 return 0;
}