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