#include <iostream>
#include <fstream>
using namespace std;
ifstream fi("fact.in");
ofstream fo("fact.out");

long nr, n, p, i, p2;
int main() {
  fi >> p;
  if (p == 0) fo << 1;
  else {
    for (nr = p;nr <= p*200;nr++) {
      p2 = 0;
      for (i = 5;i < nr;i *= 5)
        p2 += nr / i;
      if (p == p2) {
        fo << nr;
        break;
      }
      if (nr == 200 && p != p2) fo << -1;
    }
  }
}