#include<fstream.h>

int cinci(int x)
{
  long p=0;
  while(x>5)
    p+=x/5,x/=5;
  return p;
}
int main()
{
  long p,x,q;int ok=1;
  ifstream in("fact.in");
  ofstream out("fact.out");
  in>>p;
  long z=p;
  x=p*5;
  for(long i=5;;i*=5)
    {
    q=p/i;p-=q;if(q==0) break;
    while(q)
      if(x%i!=0||ok==0) x--,q--,ok=1;
       else q--,ok=0;
    }
  x=x-x%5;
  if(x==0) x=1;
  if(z!=cinci(x)) out<<-1;
   else out<<x;
  return 0;
}