# -*- coding: utf-8 -*-

N = int(raw_input())

E = [0.0 for _ in xrange(N + 1)]
for i in xrange(0, N + 1):
    for j in xrange(max(i - 6, 1), 1 + i - 1):
        E[i] += E[j] / 6
    E[i] += 1
print E[N]