from collections import *
from itertools import *
from functools import *
from heapq import *
import sys, math, random, time

K = int(input())

mem = [-1] * (K + 1)

mem[K] = 0
mem[K - 1] = 1


def f(x):
    if x >= K:
        return 0
    if mem[x] != -1:
        return mem[x]
    mem[x] = sum(f(x + i) for i in range(1, 7)) / 6 + 1
    return mem[x]


print(f(0))