import random
N=int(input())
K=int(input())
ans=0
for _ in range(5*10**5):
    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
ans/=5*10**5
print(ans)