#include <stdio.h>

FILE* f;
FILE* g;
int	n, m, s;
int	a[16][16];

int	main()
{
	f = fopen("flip.in", "r");
	g = fopen("flip.out", "w");

	fscanf(f, "%d %d", &n, &m);
	for (int i = 0; i < n; ++i)
		for (int j = 0; j < m; ++j)
			fscanf(f, "%d", &a[i][j]);

	for (int i = 0; i < n; ++i)
	{
		int sp = 0;
		int sn = 0;
		for (int j = 0; j < m; ++j)
			if (a[i][j] < 0)
				sn += a[i][j];
			else
				sp += a[i][j];
		sn *= -1;
		int d = sp - sn;
		if (d < 0) d *= -1;
		s += sp;
	}
	fprintf(g, "%d\n", s);
	return (0);
}