#include <iostream>
#include <fstream>
using namespace std;
int main()
{
	ifstream in("flip.in");
	ofstream out("flip.out");
	int tab[16][16];
	int n, m,sumL=0,sumC=0,sumT=0;
	in >> n >> m;
	for (int i = 0;i < n;i++)
		for (int j = 0;j < m;j++)
			in >> tab[i][j];
	for (int i = 0;i < n;i++)
	{
		sumL = 0;
		sumT = 0;
		for (int j = 0;j < m;j++)
		{
			sumL = sumL + tab[i][j];
			sumC = sumC + tab[j][i];
		}
		if (sumC < 0)
		{
			for (int j = 0;j < m;j++)
				tab[j][i] = (-1)*tab[j][i];
		}
		if (sumL < 0)
		{
			for (int j = 0;j < m;j++)
				tab[i][j] = (-1)*tab[i][j];
		}
		
	}
	for (int i = 0;i < n;i++)
		for (int j = 0;j < m;j++)
			sumT = sumT + tab[i][j];
	out << sumT;
	return 0;
}