#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream in;
    in.open("flip.in");
    ofstream out;
    out.open("flip.out");

    unsigned int a, b;

    in >> a >> b;

    int x[a][b], s;

    for (unsigned int i = 0; i < a; i++)
        for (unsigned int j = 0; j < b; j++)
            in >> x[i][j];

    for (unsigned int i = 0; i < a; i++)
    {
        s = 0;
        for (unsigned int j = 0; j < b; j++)
            s += x[i][j];
        if (s < 0)
            for (unsigned int j = 0; j < b; j++)
            x[i][j] *= -1;
    }


    for (unsigned int j = 0; j < b; j++)
    {
        s = 0;
        for (unsigned int i = 0; i < a; i++)
            s += x[i][j];
        if (s < 0)
        for (unsigned int i = 0; i < a; i++)
            x[i][j] *= -1;
    }

    s = 0;

    for (unsigned int i = 0; i < a; i++)
        for (unsigned int j = 0; j < b; j++)
            s += x[i][j];

    out << s;

    return 0;
}