#include <iostream>
#include <fstream>
#include <cmath>
using namespace std;
int f (int x)
{
  int i = 0;
  while (x % 5 != 0) x--;
  while (x) { x -= 5; i++; }
  return i;
}
int main()
{
  int p, m, l = 0, r = 10000;
  ifstream f("fact.in");
  ofstream g("fact.out");
  f >> p;
  while (l < r) {
    m = l + (r - l) / 2;
    if (f(m) == p) { g << m; break; }
    if (f(m) > p) l = m;
    if (f(m) < p) r = m + 1;
  }
  f.close ();
  g.close ();
  return 0;
}