#!/usr/bin/python
# -*- coding: utf-8 -*-
# †
# (ΦωΦ)＜運を天にまかせる系
from datetime import datetime, timedelta
from random import randint

start = datetime.now()
limit = timedelta(milliseconds=4949)

n = int(raw_input())
k = int(raw_input())

turn, win = 0, 0
for _ in xrange(19921223):
    turn += 1
    taro = sum(randint(1, 6) for _ in xrange(n-k)) \
         + sum(randint(4, 6) for _ in xrange(k))
    jiro = sum(randint(1, 6) for _ in xrange(n))
    if taro > jiro:
        win += 1
    now = datetime.now()
    if (now - start) >= limit:
        break
print float(win) / turn