#include <fstream>

using namespace std;

ifstream f("flip.in");
ofstream g("flip.out");

long a[17][17], b[17], k = 0;
int m, n;

long suma_poz(int x, int y)
{
	long s = 0;
	for (int i = 1; i <= m; i++)
	{
		if (a[x][i] > 0)
		{
			s += a[x][i];
		}
	}

	for (int i = 1; i <= n; i++)
	{
		if (a[i][y] > 0)
		{
			s += a[i][y];
		}
	}
	if (a[x][y] > 0)
	{
		s -= a[x][y];
	}

	return s;
}

long suma_neg(int x, int y)
{
	long s = 0;
	for (int i = 1; i <= m; i++)
	{
		if (a[x][i] < 0)
		{
			s += a[x][i];
		}
	}

	for (int i = 1; i <= n; i++)
	{
		if (a[i][y] < 0)
		{
			s += a[i][y];
		}
	}
	if (a[x][y] < 0)
	{
		s -= a[x][y];
	}

	return s;
}

void maneta(int x, int y)
{
	for (int i = 1; i <= m; i++)
	{
		a[x][i] *= -1;
	}
	for (int i = 1; i <= n; i++)
	{
		a[i][y] *= -1;
	}

	a[x][y] *= -1;
}

int main()
{
	f >> m >> n;
	for (int i = 1; i <= m; i++)
		for (int j = 1; j <= n; j++)
			f >> a[i][j];

	int gasit = 1;

	while (gasit == 1)
	{
		gasit = 0;
		for (int i = 1; i <= n; i++)
		{
			for (int j = 1; j <= n; j++)
			{
				if (suma_poz(i, j) < -1 * suma_neg(i, j))
				{
					maneta(i, j);
					gasit = 1;
				}
			}
		}

	}

	for (int i = 1; i <= m; i++)
	{
		for (int j = 1; j <= n; j++)
		{
			k += a[i][j];
		}
	}

	g << k;
	return 0;
}