#include <iostream>
#include <fstream>
using namespace std;

int test2(int a[17][17], int n, int m)
{
	int i, j, po, ne, s = 0;
	for (i = 0; i<n; i++)
	{
		po = ne = 0;
		for (j = 0; j<m; j++)
		if (a[i][j]>0)
			po = po + a[i][j];
		else ne = ne + a[i][j];
		ne = -ne;
		if (ne>po)
		for (j = 0; j < m; j++)
			s = s - a[i][j];
		else for (j = 0; j < m; j++)
			s = s + a[i][j];
	}
	return s;
}

int test1(int a[17][17], int n, int m)
{
	int i, j, po, ne;
	for (i = 0; i<n; i++)
	{
		po = ne = 0;
		for (j = 0; j<m; j++)
		if (a[j][i]>0)
			po = po + a[j][i];
		else ne = ne + a[j][i];
		ne = -ne;
		if (ne>po)
		for (j = 0; j<m; j++)
			a[j][i] = -a[j][i];
	}
	return test2(a, n, m);
}

int main()
{
	int n, m, a[17][17], i, j;
	ifstream f("flip.in");
	ofstream g("flip.out");
	f >> n; f >> m;
	for (i = 0; i<n; i++)
	for (j = 0; j<m; j++)
		f >> a[i][j];
	g << test1(a, n, m);
}