#include <fstream>



using namespace std;



ifstream in ("fact.in");

ofstream out ("fact.out");



const int VM = 5*1e8;



int nr0 (int n) {

  int nr;

  nr = 0;

  while (n >= 5)

    nr += (n /= 5);

  return nr;

}



int cbin (int p) {

  int st, dr, m;

  st = 1; dr = VM;

  while (st < dr) {

    m = (st + dr) / 2;

    if (nr0 (m) >= p)

      dr = m;

    else

      st = m + 1;

  }

  if (nr0 (st) == p)

    return st;

  return -1;

}



int main () {

  int p;

  in >> p;

  out << cbin (p);

  return 0;

}