n = int(input())
dp = [1, 0, 0, 0, 0, 0]
for _ in range(n - 1):
    for i in range(5, 0, -1):
        dp[i] *= (i + 1) / 6
        dp[i] += dp[i - 1] * (6 - i) / 6
    dp[0] /= 6
print(dp[-1])