#include <bits/stdc++.h>

int max_sum(int matrix[16][16], int m, int n) {
    
    for (int i = 0; i < m; i++) { // switching by rows 
        int sum_row = 0;
        for (int j = 0; j < n; j++) sum_row += matrix[i][j];
        if (sum_row > 0) continue;
        for (int j = 0; j < n; j++) matrix[i][j] *= -1;
    }

    for (int j = 0; j < n; j++) { // switching by columns
        int sum_col = 0;
        for (int i = 0; i < m; i++) sum_col += matrix[i][j];
        if (sum_col > 0) continue;
        for (int i = 0; i < m; i++) matrix[i][j] *= -1;
    }

    int sum = 0;
    for (int i = 0; i < m; i++) 
        for (int j = 0; j < n; j++) 
            sum += matrix[i][j];
    return sum;
}

int main() {
    std::ifstream f("flip.in");
    std::ofstream g("flip.out");
    int m, n;
    f >> m >> n;
    int matrix[16][16];
    for (int i = 0; i < m; i++)
        for (int j = 0; j < n; j++)
            f >> matrix[i][j];
    f.close();

    g << max_sum(matrix, m, n);
    g.close();
    return 0;
}