#include <fstream>
using namespace std;
long c[17],l[17];
int main()
{
    ifstream in;in.open("flip.in");
    ofstream o;o.open ("flip.out", ofstream::out);
    long M,N,f[17][17],i,j,k,flag;
    in>>N;in>>M;k=0;
    for(i=0;i<N;i++)
    {
     for(j=0;j<M;j++)
        {
            in>>f[i][j];
            c[j]=c[j]+f[i][j];
            k=k+f[i][j];
        }
        if(c[j]==0)flag=0;
    }
    if(flag==0)
    for(j=0;j<M;j++)
     {
         if(c[j]<0)
        {
         k=k-2*c[j];l[i]=0;
         for(i=0;i<N;i++)
            {
             f[i][j]= -f[i][j];
             l[i]=l[i]+f[i][j];
             if(l[i]<0){k=k-2*l[i];}
            }
        }
     }
    else
    {
        for(i=0;i<N;i++)
          if(l[i]<0)
         k=k-2*l[i];
    }
    o<<k;
    in.close();o.close();
   return 0;
   }