#!/usr/bin/python
from fractions import Fraction
k = int(raw_input())
dp = [0] * (k+1)
for i in xrange(6):
    if k-i > 0:
        dp[k-i-1] = Fraction(7, 6) ** i
for x in reversed(xrange(k-6)):
    dp[x] = sum(dp[x+1:x+7]) / 6 + 1
print float(dp[0])