import strutils, math

const
  pn6 = [2, 3, 5, 7, 11, 13]
  cn6 = [4, 6, 8, 9, 10, 12]
var
  cnt = 0
let
  K = stdin.readLine.parseInt


for p in pn6:
  for c in cn6:
    if p * c == K:
      cnt += 1

echo (cnt / pn6.len ^ 2).round(12)