#include<stdio.h>

main ()
{
	int n, m, a[15][15], i, j, s, s1=0, s2=0;
	FILE *f;
	
f = fopen("flip.in", "r");
	fscanf(f, "%d %d", &n, &m);
	for(i=0; i<n; i++)
		for(j=0; j<m; j++)
			fscanf(f, "%d", a[i][j]);
fclose(f);
	
	for(i=0; i<n; i++)
	{
		for(j=0; j<m; j++)
		{
			s1+= a[i][j];
			s2-= a[i][j];
		}		
	if(s1<s2)
		for(j=0; j<m; j++)
			a[i][j]= -a[i][j];
	if(a[i][j] > 0)	
		s+= a[i][j]; 
	}
f = fopen("flip.out", "w+");
	fprintf(f, "%d", s);
fclose(f);
}