//http://www.infoarena.ro/problema/flip

#include<stdio.h>

int main()
{
	FILE *f=fopen ("flip.in","r");
	FILE *g=fopen ("flip.out","w");
	
	long a[17][17];
	int i,j,m,n,s;
	fscanf (f,"%d %d",&m,&n);

	for (i=1;i<=m;i++)
	{
		s=0;
		for (j=1;j<=n;j++)
		{
			fscanf (f,"%d",&a[i][j]);
			s=s+a[i][j];
		}
		a[i][0]=s;
	}


	for (i=1;i<=m;i++)
	{
		if (a[i][0]<0)
			for (j=1;j<=n;j++)
				a[i][j]=a[i][j]*(-1);
	}

	for (j=1;j<=n;j++)
	{
		s=0;
		for (i=1;i<=m;i++)
			s=s+a[i][j];

		if (s<0)
			for (i=1;i<=m;i++)
			a[i][j]=a[i][j]*(-1);
	}

	s=0;
	for (i=1;i<=m;i++)
		for (j=1;j<=n;j++)
		{
			s=s+a[i][j];
		}
	fprintf (g,"%d",s);
	return 0;
}