#include<iostream.h>
#include<stdio.h>
#include<stdlib.h>
typedef long int li;
long int ma[16][16];

int main()
{
	FILE *in=fopen("flip.in","r"),
	     *out=fopen("flip.out","w");
	int n,a,i,j;
	long int s,s1;
	fscanf(in,"%d",&n);
	fscanf(in,"%d",&a);/*numarul de lini si de coloane*/





	for (i=1;i<=n;i++) 
	{
		for (j=1;j<=a;j++)
		{
	
			fscanf(in,"%l",&ma[i][j]);
	 
		}
	}


		
	for (i=1;i<=n;i++)
	{
		s=s1=0;
		for (j=1;j<=a;j++)
		{
			s+=ma[i][j];
			s1+=-ma[i][j];
		}
		if (s<s1)
		{
			
		for (j=1;j<=a;j++)
		
		{
				ma[i][j]=ma[i][j]*(-1);
			}
		}
	}
	for (j=1;j<=a;j++)
	{
	    s=s1=0;
		for (i=1;i<=n;i++)
		{
			s+=ma[i][j];
			s1+=-ma[i][j];
		}
		if (s<s1)
		{
			for (i=1;i<=n;i++)
			{
				ma[i][j]=ma[i][j]*(-1);
			}
		}
	}
		
	s=0;
	for (i=1;i<=n;i++)
	{
		for (j=1;j<=a;j++)
		{
			s+=ma[i][j];
		}
	
	}
	fprintf(out,"%l",s);

	
	return 0;

}