K = int(input())
N = 10000
P = [[0] * (K + 1) for _ in range(N + 1)]
P[0][0] = 1
for i in range(1, N + 1):
    tmp = 0
    for j in range(min(K, 5)):
        tmp += P[i - 1][K - j - 1] * (5 - j) / 6
    P[i][0] = tmp
    for j in range(1, K + 1):
        P[i][j] = sum(P[i - 1][max(0, j - 6):j]) / 6

ans = 0
for i in range(N + 1):
    ans += i * P[i][K]
print(ans)