import random
N = int(input())
K = int(input())
ans = 0
for _ in range(1000000):
    s0, s1 = 0, 0
    for i in range(N):
        s0 += random.randint(1, 6)
    for i in range(N - K):
        s1 += random.randint(1, 6)
    for i in range(K):
        s1 += random.randint(4, 6)
    if s0 < s1:
        ans += 1
print(ans / 10 ** 6)