#include <fstream>
#include <iostream>
#include <cmath>

using namespace std;

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

int a[17][17];

int main()
{
    int N, M, i, j, s1, s2, s = 0;
    in >> N >> M;
    for (i = 1; i <= N; ++i)
        for (j = 1; j <= M; ++j)
            in >> a[i][j];
    in.close();

    for (i = 1; i <= N; ++i)
    {
        s1 = 0;
        s2 = 0;
        for (j = 1; j <= M; ++j)
        {
            if (a[i][j] >= 0)
                s1 += a[i][j];
            else
                s2 += a[i][j];
        }
        if (abs(s2) > s1)
        {
            for (j = 1; j <= M; ++j)
                a[i][j] = -a[i][j];
        }
    }

    for (j = 1; j <= M; ++j)
    {
        s1 = 0;
        s2 = 0;
        for (i = 1; i <= N; ++i)
        {
            if (a[i][j] >= 0)
                s1 += a[i][j];
            else
                s2 += a[i][j];
        }
        if (abs(s2) > s1)
        {
            for (i = 1; i <= N; ++i)
                a[i][j] = -a[i][j];
        }
    }

    s = 0;
    for (i = 1; i <= N; ++i)
        for (j = 1; j <= M; ++j)
            s += a[i][j];

    out << s << '\n';
    out.close();
    return 0;
}