#include<stdio.h>

long n,m,a[20][20],i,j,s1,s2,k;

int main()
{
	freopen("flip.in","r",stdin);
	freopen("flip.out","w",stdout);
	
	scanf("%ld%ld",&n,&m);
	
	for(i=1;i<=n;i++)
		for(j=1;j<=m;j++)
			scanf("%ld",&a[i][j]);
		
	for(i=1;i<=n;i++)
	{
		for(j=1;j<=m;j++)
			{
			if(a[i][j]>0)
				s1+=a[i][j];
			else
				s2+=(a[i][j]*-1);
		    }
		if(s2>s1)
		   for(k=1;k<=m;k++)
			   a[i][k]*=-1;
		s1=0;s2=0;   
	}
	
	s1=0;s2=0;   
	for(i=1;i<=m;i++)
	{
		for(j=1;j<=n;j++)
			{
			if(a[j][i]>0)
				s1+=a[j][i];
			else
				s2+=(a[j][i]*-1);
		    }
		if(s2>s1)
		   for(k=1;k<=n;k++)
			   a[k][i]*=-1;
		s1=0;s2=0;   
	}
	
	s1=0;s2=0;
	for(i=1;i<=n;i++)
		for(j=1;j<=m;j++)
			s1+=a[i][j];
		
	printf("%ld",s1);
    return 0;
}