import random
n=int(input())
k=int(input())
ans=0
for _ in range(10**6):
    a,b=0,0
    for _ in range(n):
        a+=random.randint(1,6)
    for _ in range(n-k):
        b+=random.randint(1,6)
    for _ in range(k):
        b+=random.randint(4,6)
    if a<b:
        ans+=1
ans/=10**6
print(ans)