#include <fstream>
using namespace std;

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

int main()
{
	long n,m,a[17][17];
	f>>n>>m;

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

	for (int i=1; i<=n; ++i)
	{
		int S=0;
		for (int j=1; j<=m; ++j)
		{
			S+=a[i][j];
		}

		if (S<0)
		{
			for (int j=1; j<=m; ++j)
				a[i][j]*=-1;
		}
	}

	for (int j=1; j<=m; ++j)
	{
		int S=0;
		for (int i=1; i<=n; ++i)
		{
			S+=a[i][j];
		}

		if (S<0)
		{
			for (int i=1; i<=n; ++i)
				a[i][j]*=-1;
		}
	}

	int S=0;
	for (int i=1; i<=n; ++i)
		for (int j=1; j<=m; ++j)
			S+=a[i][j];
	
	g<<S;
	g.close();
	return 0;
}