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

K = int(input())

dp = [-1]*(K+6)
def E(x):
    if dp[x] >= 0:
        return dp[x]

    prob = -1
    if x >= K:
        prob = 0
    else:
        prob = (E(x+1)*1/6+E(x+2)*1/6+E(x+3)*1/6+E(x+4)*1/6+E(x+5)*1/6+E(x+6)*1/6+1)
    
    dp[x] = prob
    return dp[x]

print(E(0))