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

int n, m, tabla[17][17];
bool ok = false;
int minNeg_l = 0, maxNeg_c = 0, suma = 0;

int main()
{
	int i, j;

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

	fin >> n >> m;
	for (i = 1; i <= n; i++)
		for (j = 1; j <= m; j++) {
			fin >> tabla[i][j];
			suma += tabla[i][j];
			if (tabla[i][j] < 0) {
				tabla[i][0]++;
				tabla[0][j]++;
				ok = true;	//am gasit numere negative
			}
		}

    if(ok) {
        for (i = 1; i <= m; i++)
            if(tabla[0][i] > tabla[0][maxNeg_c])
                maxNeg_c = i;

        for (i = 1; i <= n; i++)
            tabla[i][maxNeg_c] *= 1;

        tabla[0][0] = n + 1;
        for (i = 1; i <= n; i++)
            if(tabla[i][0] < tabla[minNeg_l][0] and tabla[i][0] > 0)
                minNeg_l = i;

        for (i = 1; i <= n; i++)
            tabla[minNeg_l][i] *= 1;

        suma = 0;
        for (i = 1; i <= n; i++)
            for (j = 1; j <= m; j++)
                suma += tabla[i][j];
        fout << suma;
    }
    else
        fout << suma;

	fin.close();
	fout.close();

	return 0;
}