#int(input())
#map(int, input().split())
#list(map(int, input().split()))

K = int(input())
dp = [0] * 30

dp[0] = 1
for i in range(K-1, -1, -1):
    a = 0
    for j in range(6):
        a += dp[i+j+1]
    dp[i] = a/6 + 1

print(dp[0])