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

// modifica numele fisierelor

ifstream cin("flip.in");
ofstream cout("flip.out");

int main()
{
    short n, m, i, j;
    cin >> n >> m;
    int mat[n][m], sum, sumc;

    sumc = sum = 0;

    for (i = 0; i < n; i++)
        for (j = 0; j < m; j++)
            cin >> mat[i][j];

    for (i = 0; i < n; i++)
    {
        sumc = 0;

        for (j = 0; j < m; j++)
            sumc +=  mat[i][j];

        if (sumc < 0)
        {
            for (j = 0; j < m; j++)
                mat[i][j ]= -mat[i][j];
        }   
    }

    for (i = 0; i < m; i++)
    {
        sumc = 0;

        for (j = 0; j < n; j++)
            sumc +=  mat[j][i];

        if (sumc < 0)
            for (j = 0; j < n; j++)
                mat[j][i] =  -mat[j][i];
    }

    for (i = 0; i < n; i++)
        for (j = 0; j < m; j++)
            sum += mat[i][j];

    cout << sum;
    
    return 0;
}