from random import randrange
INF = 10**6
N = int(input())
K = int(input())
cnt = 0
for _ in range(INF):
    A = 0
    B = 0
    for i in range(N):
        A += randrange(1,7)
    for i in range(N-K):
        B += randrange(1,7)
    for i in range(K):
        B += randrange(4,7)
    if A < B:
        cnt += 1
print(cnt / INF)