#include <fstream>

using namespace std;
int n,m,a[20][20];


void Citire()
{
    int i,j,x;
    ifstream fin("flip.in");
    fin>>n>>m;
    for(i=1;i<=n;i++)
        for(j=1;j<=m;j++)
            fin>>a[i][j];
    fin.close();
}
int Calculeaza()
{
    int i,j,s;
    s = 0;
    for(i=1;i<=n;i++)
        for(j=1;j<=m;j++)
            s+=a[i][j];
    return s;
}

ofstream fout("flip.out");
int main()
{
    int i,j,smax,s;
    Citire();
    smax = Calculeaza();
    bool ok = true;
    while(ok==true)
    {
        for(i=1;i<=m;i++)
        {
            s = 0;
            for(j=1;j<=n;j++)   s+=a[j][i];
            if(s<0)
                for(j=1;j<=n;j++) a[j][i]*=-1;
        }

        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;
        }

        s = Calculeaza();
        if(s>smax) smax = s;
        else ok = false;
    }
    fout<<smax<<"\n";

    fout.close();
    return 0;
}