#include<fstream>
using namespace std;
int main()
{
 ifstream in("flip.in");
 ofstream out("flip.out");
 int n,m,i1,i2,i3;
 in>>n>>m;
 long v[n][m],sp,sn;
 for(i1=0;i1<n;++i1)
 for(i2=0;i2<m;++i2)
 in>>v[i1][i2];
 for(i2=0;i2<m;++i2)
 {
  sp=0; sn=0;
   for(i1=0;i1<n;++i1)
   {
    sp+=v[i1][i2]; sn-=v[i1][i2];
     if(sn>sp)
     {
       for(i3=0;i3<n;++i3)
       v[i3][i2]*=-1;
      }
    }
  }
 for(i1=0;i1<n;++i1)
 {
   sp=0; sn=0;
     for(i2=0;i2<m;++i2)
     {
      sp+=v[i1][i2]; sn-=v[i1][i2];
        if(sn>sp)
       {
         for(i3=0;i3<m;++i3)
         v[i1][i3]*=-1;
         }
      }
   }
 sp=0;
 for(i1=0;i1<n;++i1)
 for(i2=0;i2<m;++i2)
 sp+=v[i1][i2];
 out<<sp;
}