// No.211 素数サイコロと合成数サイコロ (1)
package main

import "fmt"

func main() {
	var k int
	fmt.Scan(&k)
	var s = []int{2, 3, 5, 7, 11, 13}
	var g = []int{4, 6, 8, 9, 10, 12}

	match := 0
	for i := 0; i < len(s); i++ {
		for j := 0; j < len(g); j++ {
			if s[i]*g[j] == k {
				match++
			}
		}
	}
	fmt.Printf("%.18f\n", float64(match)/float64(36))
}