#!/usr/bin/python2
# -*- coding: utf-8 -*-
# †
def nCr(n, r):
    assert 0 <= r <= n
    k = r if r <= n-r else n-r
    res = 1
    for i in xrange(k):
        res *= n-i
        res /= i+1
    return res


def complete_prob(k, n):
    return float(sum((-1)**(k-i) * nCr(k-1, i-1) * (float(i)/k)**(n-1) for i in xrange(1, k+1)))

n = int(raw_input())
res = complete_prob(6, n)
print res