#include <algorithm>

using namespace std ;

int main() {
  freopen("fact.in","r",stdin) ;
  freopen("fact.out","w",stdout) ;

  int p ;
  scanf ("%d" , &p) ;

  int s=0 , x;

  for (int i=4*p ; i<=5*p ; ++i) {
    x=i ;
    s=0 ;
    while (x) {
      s+=x/5 ;
      x/=5 ;
    }
    if (s==p) {
      printf ("%d" , i) ;
      break ;
    }
    if (s>p) {
      printf ("-1") ;
      break ;
    }
  }

  return 0;
}