#include<stdio.h>
#include<fstream.h>

int n,m,i,j;
long int a[16][16],S1,S2,S;

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

int main()
{
	fscanf(fin,"%d",&n);
	fscanf(fin,"%d",&m);
	
	for(i=1;i<=n;i++)
		for(j=1;j<=m;j++)
		{
			fscanf(fin,"%ld",&a[i][j]);			
		}

	for(i=1;i<=n;i++)
	{ S1=0;
	  S2=0;
       for(j=1;j<=m;j++)
	   {
		   S1=S1+a[i][j];
		   S2=S2+(-1*a[i][j]);
		   
	   }
    if(S1<S2)
	{
	  for(j=1;j<=m;j++)
		  a[i][j]=(a[i][j]*(-1));
	}
	}
	for(j=1;j<=m;j++)
	{ S1=0;
	  S2=0;
		for(i=1;i<=n;i++)
		{
			S1=S1+a[i][j];
			S2=S2+(-1*a[i][j]);
		}
		if(S1<S2)
		{
			for(i=1;i<=n;i++)
				a[i][j]=((a[i][j]*(-1)));
		}
	}
	S=0;
	for(i=1;i<=n;i++)
	{
		for(j=1;j<=m;j++)
		{
			S=S+a[i][j];
		}
	}
		fprintf(fout,"%ld",S);
		fclose(fin);
		fclose(fout);
		return 0;
	
 	
}