#include <iostream>
#include<fstream>
using namespace std;
int n,nr,i;
int main()
{
  ifstream f("fact.in");
  ofstream g("fact.out");
    f>>n;
    i=1;
  while(i<n)
  {

   while(i%5==0) {nr=nr+1;i=i/5;}
   nr=nr+1;
   i=nr;
  }
  if(i==n) g<<i*5;
  else g<<-1;
  f.close();
  g.close();
  return 0;
}