#include <fstream>
#define NM 20

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

void bkt(int k);
int suma();
void read();

int n, m, a[NM][NM],Smax;

int main()
{
	read();
	Smax = 0;
	bkt(1);
	fout << Smax << '\n';
	return 0;


}

void read()
{
	fin >> n >> m;
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= m; j++)
			fin >> a[i][j];
}

int suma()
{
	int x = 0;
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= m; j++)
			x += a[i][j];
	return x;
}

void bkt(int k)
{
	if (k == n * m + 1)
	{
		int S;
		S = suma();
		if (S > Smax)
			Smax = S;
	}
	else {
		int l, c;
		l = k / m + 1;
		c = k % m;
		bkt(k + 1);
		a[l][c] = -a[l][c];
		bkt(k + 1);
	}
}