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