#include <iostream>
#include <fstream>
using namespace std;
ifstream f("flip.in");
ofstream g("flip.out");
int n,m,i,a[20][20],s,j;
int main()
{
   f>>n>>m;
   for(i=1;i<=n;++i)
       for(j=1;j<=m;++j)
        f>>a[i][j];
    for(i=1;i<=n;++i)
    {
        s=0;
        for(j=1;j<=m;++j)
            s=s+a[i][j];
        if(s<0)
        {
            for(j=1;j<=m;++j)
                a[i][j]=-1*a[i][j];
        }
    }
    for(j=1;j<=m;++j)
    {
        s=0;
        for(i=1;i<=n;++i)
            s=s+a[i][j];
        if(s<0)
        {
            for(i=1;i<=n;++i)
                a[i][j]=-1*a[i][j];
        }
    }
    s=0;
   for(i=1;i<=n;++i)
    {
        for(j=1;j<=m;++j)
            s=s+a[i][j];
    }
    g<<s;
    return 0;
}