#include <stdio.h>

int main()
{
	FILE *fin = fopen("flip.in","rb");
	FILE *fout = fopen("flip.out","wb");

	int n,m;
	fscanf(fin,"%d %d", &n, &m);
	int suma = 0;
	int v[n][m];
	for (int i=0;i<n;i++)
	{
		int s = 0;
		int nr_neg=0;
		int nr_poz=0;
		for (int j=0;j<m;j++)
		{
			fscanf(fin,"%d ",&v[i][j]);
			s += v[i][j];
			if (v[i][j]<0) nr_neg++;
			if (v[i][j]>0) nr_poz++;
		}
		if ((nr_neg==nr_poz && s<0) || (nr_neg > nr_poz))
			for (int j=0;j<m;j++)
			{
				v[i][j] = (-1)*v[i][j];
			}
	}

	for (int j=0;j<m;j++)
	{
		int s = 0;
		for (int i=0;i<n;i++)
		{
			s += v[i][j];
		}
		if (s<0) s = s * (-1);
		suma += s;
	}

	fprintf(fout,"%d\n", suma);
	return 0;
}