#include<iostream>
    #include<fstream>
 using namespace std;   
main()
 { int p, n, i, aux, a;

  ifstream f("fact.in");
   f>>p;
aux=p;
for(i=1;i<(p*5);i++)
{ if(i%25==0) aux--;
 if(i%125==0) aux=aux-2;
 if(i%625==0) aux=aux-3;
}
a=aux;
f.close();
 ofstream g("fact.out");
  if(a==0) g<<-1;
  else g<<a*5;
  g.close();
  return 0;
  }