#include<stdio.h>
FILE *in=fopen("flip.in","r");
FILE *out=fopen("flip.out","w");
long int n,m,i,j,a[20][20],s;
int main()
{
	fscanf(in,"%ld",&n);
	fscanf(in,"%ld",&m);
	for(i=1;i<=n;i++)
		for(j=1;j<=m;j++)
			fscanf(in,"%ld",&a[i][j]);
	for(i=1;i<=n;i++)
	{
		s=0;
		for(j=1;j<=m;j++)
			s=s+a[i][j];
		if(s<0)
			for(j=1;j<=m;j++)
				a[i][j]=a[i][j]*(-1);
	}
	for(i=1;i<=m;i++)
	{
		s=0;
		for(j=1;j<=n;j++)
			s=s+a[j][i];
		if(s<0)
			for(j=1;j<=m;j++)
				a[j][i]=a[j][i]*(-1);
	}
	s=0;
	for(i=1;i<=n;i++)
		for(j=1;j<=m;j++)
			s=s+a[i][j];
	fprintf(out,"%ld",s);
	return 0;
}