import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

N = int(read())

dp = [0] * (N+1) # 残り距離 -> 回数
for n in range(1,N+1):
    left = n - 6
    if left < 0:
        left = 0
    dp[n] = 1 + sum(dp[left:n]) / 6

answer = dp[-1]
print(answer)