#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("flip.in");
ofstream fout("flip.out");

int v[16][16];

int main()
{
	int n, m;
	fin >> n >> m;
	int sumaCol, sumaLin, sumaTot;

	sumaCol = 0;
	sumaLin = 0;
	sumaTot = 0;


	for (int i = 0; i < n; i++)
	{
		for (int j = 0; j < m; j++)
		{
			in >> v[i][j];
		}
	}

	for (int i = 0; i < n; i++)
	{
		sumaCol = 0;
		for (int j = 0; j < m; j++)
			sumaCol += v[i][j];

		if (sumaCol < 0)
		{
			for (int j = 0; j < m; j++)
			{
				v[i][j] = 0 - v[i][j];
			}
		}
	}

	for (int i = 0; i < m; i++)
	{
		sumaLin = 0;
		for (int j = 0; j < n; j++)
		{
			//cout << v[j][i] << " ";
			sumaLin += v[j][i];
		}
		//cout << endl;

		if (sumaLin < 0)
		{
			for (int j = 0; j < n; j++)
			{
				v[j][i] = 0 - v[j][i];
			}
		}
	}

	for (int i = 0; i < n; i++)
	{
		for (int j = 0; j < m; j++)
		{
			//cout << v[i][j] << " ";
			sumaTot += v[i][j];
		}
		//cout << endl;
	}

	fout << sumaTot;
}