#include <bits/stdc++.h>
using namespace std;
#define NMAX 1005
#define MOD 1009

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

int n, m;
int ma[40][40];
unsigned long long int suma;
int main()
{
    fin >> n >> m;
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
        {
            fin >> ma[i][j];
        }
    }
    for (int i = 1; i <= n; i++)
    {
        long long int suma_coloana = 0;
        for (int j = 1; j <= m; j++)
        {
            suma_coloana += ma[i][j];
        }
        if (suma_coloana < 0)
        {
            for (int j = 1; j <= m; j++)
            {
                ma[i][j] *= -1;
            }
        }
    }
    for (int j = 1; j <= m; j++)
    {
        long long int suma_linie = 0;
        for (int i = 1; i <= n; i++)
        {
            suma_linie += ma[i][j];
        }
        if (suma_linie < 0)
        {
            for (int i = 1; i <= n; i++)
            {
                ma[i][j] *= -1;
            }
        }
    }
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
        {
            suma += ma[i][j];
        }
    }
    fout << suma;
    fin.close();
    fout.close();
    return 0;
}