K = int(input())
dp = [1000000] * (K + 6)
for i in range(K, K + 6):
    dp[i] = 0
for i in range(K - 1, -1, -1):
    x = 1
    for j in range(1, 7):
        x += dp[i + j] / 6
    dp[i] = x
print(dp[0])