#include <fstream>
using namespace std;
ifstream cin("fact.in");
ofstream cout("fact.out");
int p;
long long nz(long long n) {
  int cnt = 0;
  int p = 5;
  while (p <= n) {
    cnt += n / p;

    p *= 5;
  }
  return cnt;
}
int main() {

  cin >> p;
  long long st = 1;
  long long dr = 1e9;
  long long mij;
  while (st <= dr) {
    mij = (st + dr) / 2;
    if (nz(mij) < p) {
      st = mij + 1;

      
    } else {
      dr = mij - 1;
    }
  }
  if(nz(st) == p)cout<<st;
  else cout<<-1;
}