#include <iostream>
#include <fstream>
#include <vector>

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

int N, M;

int main() {
    fin >> N >> M;

    std::vector<std::vector<int>> a(N, std::vector<int>(M));


    for (int i = 0; i < N; i++)
        for (int j = 0; j < M; j++)
            fin >> a[i][j];


    for (int i = 0; i < N; i++) {
        int suma = 0;
        for (int j = 0; j < M; j++)
            suma += a[i][j];
        if (suma < 0) {
            for (int j = 0; j < M; j++)
                a[i][j] *= -1;
        }
    }

    for (int j = 0; j < M; j++) {
        int suma = 0;
        for (int i = 0; i < N; i++)
            suma += a[i][j];
        if (suma < 0) {
            for (int i = 0; i < N; i++)
                a[i][j] *= -1;
        }
    }

    int suma = 0;
    for (int i = 0; i < N; i++)
        for (int j = 0; j < M; j++)
            suma += a[i][j];

    fout << suma;

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

    return 0;
}