def solve():
    K = int(input())

    p = [0] * (K + 1)

    p[0] = 1
    for i in range(1, K + 1):
        s = max(0, i - 6)
        p[i] = sum(p[j] / 6 for j in range(s, i))

    ek = 7 ** (K - 1) / 6 ** (K - 1)
    print('{:.5f}'.format(ek / p[K]))


if __name__ == '__main__':
    solve()