#include <iostream>
#include <fstream>

using namespace std;

int n,m,a[17][17];
long long s;

int main()
{
    int i,j;
    freopen("flip.in","r",stdin);
    freopen("flip.out","w",stdout);
    cin>>n>>m;
    for(i=1;i<=n;i++)
    {
        s=0;
        for(j=1;j<=m;j++)
        {
            cin>>a[i][j];
            s+=a[i][j];
        }
        if(s<0)
        for(j=1;j<=m;j++)
        {
            a[i][j]=-a[i][j];
        }
    }
    for(j=1;j<=m;j++)
    {
        s=0;
        for(i=1;i<=n;i++)
        {
            s+=a[i][j];
        }
        if(s<0)
        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];//,cout<<a[i][j]<<" ";
       // cout<<"\n";
    }
    cout<<s<<"\n";
    return 0;
}