#include <fstream>

using namespace std;

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

int m,n,a[20][20],i,j,s,t;

int main()
{
    fin >> n >> m;
    for (i=1;i<=n;++i)
    {
        for (j=1;j<=m;++j)
        {
            fin>>a[i][j];
        }
    }

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

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

    for (i=1;i<=n;++i)
    {
        for (j=1;j<=m;++j)
        {
            t+=a[i][j];
        }
    }

    fout << t;



    return 0;
}