#include <stdio.h>
int a[260],n,m,sum[260],suma;
void citire()
{
	int i;
	scanf("%d%d",&n,&m);
	for (i=1; i<=n*m; i++)
	{
		scanf("%d",&a[i]);
		suma+=a[i];
	}
}
void sume()
{
	int i,j;
	for (i=1; i<=m; i++)
	{
		for (j=i; j<=m*n; j+=n)
			sum[i]+=a[j];
		if (sum[i]<=0)
			suma+=2*sum[i]*-1;
	}
}
/*void schimbare()
{
	int i,j,spart=0;
	for (i=1; i<=m; i++)
	{
		for (j=i; j<=m*n; j+=n)
			spart+=-a[j];
		if (spart>sum[i])
			suma+=spart-sum[i];
	}
}*/
int main()
{
	freopen("flip.in","r",stdin);
	freopen("flip.out","w",stdout);
	citire();
	sume();
	//schimbare();
	printf("%d",suma);
	return 0;
}