#include <fstream>

using namespace std;

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

void comuta(int n,int m,int v[][17], int l, int c)
{
	if (l != 0)
		for (int i = 1; i <= m; i++)
			v[l][i] *= -1;
	else
		for (int i = 1; i <= n; i++)
			v[i][c] *= -1;
}

int suma(int n, int m, int v[][17])
{
	int s = 0;
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= m; j++)
			s += v[i][j];
	return s;
}

int main()
{
	int n, m, v[17][17];
	fin >> n >> m;
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= m; j++)
			fin >> v[i][j];
	int smax = suma(n, m, v);
	for (int i = 1; i <= n; i++)
	{
		for (int j = 1; j <= m; j++)
		{
			comuta(n, m, v, 0, j);
			if (smax < suma(n, m, v))
				smax = suma(n, m, v);
			else
				comuta(n, m, v, 0, j);
		}
		comuta(n, m, v, i, 0);
		if (smax < suma(n, m, v))
			smax = suma(n, m, v);
		else
			comuta(n, m, v, i, 0);
	}
	
	fout << smax;
	fin.close();
	fout.close();
	return 0;
}