#include <iostream>
#include <fstream>

using namespace std;

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

int absValue(int p)
{
    if ( p > 0 )
        return -p;
    if ( p < 0 )
        return p;
}

int main()
{
    int N, M, a[16][16], lin[16], col[16];
    f >> N >> M;
    for ( int i = 1; i <= N; i++ )
    {
        lin[i] = 0;
        for ( int j = 1; j <= M; j++ )
        {
            f >> a[i][j];
            lin[i] = lin[i] + a[i][j];
        }
    }
    for ( int j = 1; j <= M; j++ )
    {
        col[j] = 0;
        for ( int i = 1; i <= N; i++ )
        {
            col[j] = col[j] + a[i][j];
        }
    }
    for ( int x = 1; x <= max(N,M); x++ )
    {
        if ( col[x] < 0 )
        {
            for ( int i = 1; i <= M; i++ )
            {
                a[i][x] = absValue(a[i][x]);
            }
        }
        if ( lin[x] < 0 )
        {
            for ( int j = 1; j <= N; j++ )
            {
                a[x][j] = absValue(a[x][j]);
            }
        }
    }
    int sum = 0;
    for ( int i = 1; i <= N; i++ )
    {
        for ( int j = 1 ; j <= M; j++ )
        {
            sum += a[i][j];
        }
    }
    o << sum;
    return 0;
}