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

ifstream f("flip.in");
ofstream g("flip.out");
int a[17][17],s=0;
int main()
{   
	int m=0, n=0;
	f >> m;
	f >> n;
	for (int i = 0; i < m; i++)
	{
		for (int j = 0; j < n; j++)
			f >> a[i][j];
	}
	for (int i = 0; i < m; i++)
	{
		int sum = 0;
		for (int j = 0; j < n; j++)
			sum += a[i][j];
		if (sum < 0)
			for (int j = 0; j < n; j++)
				a[i][j] *= -1;
	}
	for (int i = 0; i < n; i++)
	{
		int sum = 0;
		for (int j = 0; j < m; j++)
			sum += a[j][i];
		if (sum < 0)
			for (int j = 0; j < m; j++)
				a[j][i] *= -1;
	}
	for (int i = 0; i < m; i++)
		for (int j = 0; j < n; j++)
			s += a[i][j];
	g << s;


	return 0;
}