#include<stdio.h>
FILE *f,*g;
int N,M,i,j,s;
long c[16][16];
int main ()
{
  f=fopen("flip.in","r");
  g=fopen("flip.out","w");
  fscanf(f,"%d%d",&N,&M);
  for (i=0;i<N;i++)
    {
      for (j=0;j<M;j++)
	{
	  fscanf(f,"%d",&c[i][j]);
	}
    }
  for (i=0;i<N;i++)
    {
      s=0;
      for (j=0;j<M;j++) s+=c[i][j];
      if (s<0)
	{
	  for (j=0;j<M;j++) c[i][j]=-c[i][j];
	}
    }
  for (j=0;j<M;j++)
    {
      s=0;
      for (i=0;i<N;i++) s+=c[i][j];
      if (s<0)
	{
	  for (i=0;i<N;i++) c[i][j]=-c[i][j];
	}
    }
  s=0;
  for (i=0;i<N;i++)
    {
      for (j=0;j<M;j++) s+=c[i][j];
    }
  fprintf(g,"%d",s);
  /*for (i=0;i<N;i++)
    {
      for (j=0;j<M;j++) fprintf(g,"%d ",c[i][j]);
      fprintf(g,"\n");
    }*/
  fcloseall();
  return 0;
}