from typing import List, Tuple, Callable, TypeVar
import sys
import itertools
import heapq
import bisect
import math
from collections import deque, defaultdict, Counter
from functools import lru_cache, cmp_to_key

input = sys.stdin.readline

if __file__ != 'prog.py':
    sys.setrecursionlimit(10 ** 6)


def readints(): return map(int, input().split())
def readlist(): return list(readints())
def readstr(): return input()[:-1]


K = int(input())

dp = [0] * (K + 10)
for i in range(K)[::-1]:
    dp[i] = sum(dp[i + 1:i + 6 + 1]) / 6 + 1
print(dp[0])