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