#include <iostream>
#include <fstream>
using namespace std;
int n,i,j,m,v[100],s1,s2,sfinal;
int main()
{
    ifstream f("flip.in");
    ofstream g("flip.out");
    f>>n>>m;
    for (i=1;i<=n;i++)
    {
        for (j=1;j<=m;j++)
        {
            f>>v[j];
        }
    }
    for (i=1;i<=n;i++)
    {
        for (j=1;j<=n;j++)
        {
            s1=s1+v[j];
            if (s1<0)
            {
               for (j=1;j<=m;j++) v[j]=v[j]*-1;
            }
            s1=0;
        }
    }
    for (j=1;j<=m;j++)
    {
        for (i=1;i<=n;i++)
        {
            s2=s2+v[i];
            if (s2<0)
            {
               for (i=1;i<=n;i++) v[i]=v[i]*-1;
            }
            s2=0;
        }
    }
    for (i=1;i<=n;i++)
    {
        for (j=1;j<=m;j++)
        {
            sfinal=sfinal+v[j];
        }
    }
    g<<sfinal;
    return 0;
}