#include <stdio.h>
int main()
{
int v[16][16];
long long int a,b,sumb[16],sumbinv[16],suma[16],sumainv[16],M,N,rez;
freopen ("flip.in","r",stdin);
freopen ("flip.out","w",stdout);
scanf ("%lld",&N);
scanf ("%lld",&M);

//citim valorile
//a inseamna linia si b inseamna coloana
for (a=1;a<=N;a++)
	{
	suma[a]=0;
	sumainv[a]=0;
	for (b=1;b<=M;b++)
		{
		scanf ("%d",&v[a][b]);
		suma[a]=suma[a]+v[a][b];
		sumainv[a]=sumainv[a]-v[a][b];
		}
	}

a=1;
while (a<=N) //verificam liniile
	{
	if (suma[a]<sumainv[a])
		{
		for (b=1;b<=M;b++)
			{
			v[a][b]=v[a][b]*(-1);
			}
		}
	a++;
	}



a--;
b=1;
while (b<=M)
	{
	a=1;sumb[b]=0;
	while (a<=N)
		{
		sumb[b]=sumb[b]+v[a][b];
		a++;
		}
	b++;
	}
b=1;
for (b=1;b<=M;b++) //verificam coloanele
	{
	if (sumb[b]<sumb[b]*(-1))
		{
		for (a=1;a<=N;a++)
			{
			v[a][b]=v[a][b]*(-1);
			}
		}

	}
//printf("%lld\n",a);
rez=0;
for (a=1;a<=N;a++)
	{
	for (b=1;b<=M;b++)
		{
		rez=rez+v[a][b];
		}
	}
printf ("%lld",rez);
return 0;
}