from time import time
from random import randint as ri

N=int(input())
K=int(input())

START=time()
TIME_LIMIT=4.6

Battle=0
Win=0
while time()-START<=TIME_LIMIT:
    Battle+=1

    A=B=0
    for i in range(N):
        A+=ri(1,6)

    for i in range(N):
        if i<K:
            B+=ri(4,6)
        else:
            B+=ri(1,6)

    if A<B:
        Win+=1

print(Win/Battle)