package main

import . "fmt"

func main() {
	var a,b,k int
	Scan(&k)
	for _,i:=range []int{2,3,5,7,11,13} {
		for _,j:=range []int{4,6,8,9,10,12} {
			a++
			if i*j==k {
				b++
			}
		}
	}
	Printf("%15.13f\n",float64(b)/float64(a))
}