#!/usr/bin/env python
# -*- coding: utf-8 -*-

k = int(input())

m = [0] + [pow(7.0 / 6, i - 1) for i in range(1, 8)]
append = m.append
for i in range(8, k + 1):
    append((m[i - 6] + m[i - 5] + m[i - 4] + m[i - 3] + m[i - 2] + m[i - 1]) / 6.0 + 1)
print(m[k])