#include<fstream.h>
int g1,w,i,x,y;
int main()
{
  ifstream f("energii.in");
  ofstream g("energii.out");
   f>>g1;
   f>>w;
  for(i=1;i<=g1;i++)
    f>>x>>y;
  g<<"-1";
 return 0;
}