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

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

int main() {
    int a, b, A[100][100], i, j;
    fin >> a >> b;

    for (i = 1; i <= a; i++) {
        for (j = 1; j <= b; j++) {
            fin >> A[i][j];
        }
    }

    for (j = 1; j <= b; j++) {
        int s = 0;
        for (i = 1; i <= a; i++) {
            s += A[i][j];
        }

        if (s < 0) {
            for (i = 1; i <= a; i++) {
                A[i][j] = -A[i][j];
            }
        }
    }

    for (i = 1; i <= a; i++) {
        int t = 0;
        for (j = 1; j <= b; j++) {
            t += A[i][j];
        }

        if (t < 0) {
            for (j = 1; j <= b; j++) {
                A[i][j] = -A[i][j];
            }
        }
    }

    int maxSum = 0;
    for (i = 1; i <= a; i++) {
        for (j = 1; j <= b; j++) {
            maxSum += A[i][j];
        }
    }

    fout << maxSum << endl;
    return 0;
}