#!/usr/bin/python
from itertools import product
from collections import defaultdict
from operator import mul
a = [2, 3, 5, 7, 11, 13]
b = [4, 6, 8, 9, 10, 12]
p, c = map(int, raw_input().split())
L = [a] * p + [b] * c
pro1 = defaultdict(int)
for s in product(*L):
    pro1[reduce(mul, s)] += 1
res = sum(k*v for k, v in pro1.items())
print float(res) / (6**(p+c))