#include <stdio.h>

int main()
{
	FILE *f=fopen("flip.in","r");
	FILE *g=fopen("flip.out","w");
	
	int n,m,i,j,s,S=0,a[16][16];
	
	fscanf(f,"%d%d",&n,&m);
	for (i=1;i<=n;i++)
	{ s=0;
		for (j=1;j<=m;j++)
		{fscanf(f,"%d",&a[i][j]); s+=a[i][j];}
		
		if (s<0)
		{
			for (j=1;j<=m;j++)
			{a[i][j]=a[i][j]*(-1);}
		}
	}
	
	for (j=1;j<=m;j++)
	{ s=0;
		for (i=1;i<=n;i++)
		{
			s+=a[i][j];
		}
		
		if (s<0)
		{
			for (i=1;i<=n;i++)
			{a[i][j]=a[i][j]*(-1);}
		}
	}
	
	for (i=1;i<=n;i++)
	{
		for (j=1;j<=m;j++)
		{S+=a[i][j];}
	}
	
	fprintf(g,"%d\n",S);
	
	fclose(f);
	fclose(g);
	return 0;
}