#include<stdio.h>
#include<stdlib.h>
int main()
{
	FILE *f,*g;
	f=fopen("flip.in","r");
	g=fopen("flip.out","w");
	int N,M;
	fscanf( f, "%d", &N); 
	fscanf( f, "%d", &M);
	int i,j;
	long int **a;
	a=(long**)malloc(N*sizeof(long));
	for(int i=1;i<=N;i++)
		a[i]=(long*)malloc(M*sizeof(long));
	for( i=1;i<=N;i++)
		for( j=1;j<=M;j++)
			fscanf( f,"%ld", &a[i][j]);
	
	int s=0;
	for(i=1;i<=N;i++)
	{
		for(j=1;j<=M;j++)
			s+=a[i][j];
		if(s<0)
			for(j=1;j<=M;j++)
				a[i][j]*=-1;
		s=0;
	}
	for(j=1;j<=M;j++)
	{
		for(i=1;i<=N;i++)
			s+=a[i][j];
		if(s<0)
			for(i=1;i<=N;i++)
				a[i][j]*=-1;
		s=0;
	}
	for(i=1;i<=N;i++)
		for(j=1;j<=M;j++)
			s+=a[i][j];
	fprintf( g, "%d", s);
	fclose(f);
	fclose(g);
	return 0;
}