P1_3 = 1.quo(3)
P1_2 = 1.quo(2)
pp, q = gets.split.map(&:to_i)

dp = Array.new(101 + 2, 0) # dp[i] = i% skills
dp[101] = 1.quo(3) # win
dp[102] = 1.quo(3) # lose
dp[pp] = 1.quo(3) # draw(plain) 

100.times do |i|
    ndp = Array.new(103,0r)
    ndp[101] = dp[101]
    ndp[102] = dp[102]
    (0 .. 100).each do |i|
        # unuse 
        if i + q > 100
            ndp[100] += dp[i] * (100 - i).quo(100) * P1_3
            ndp[101] += dp[i] * (100 - i).quo(100) * P1_3
            ndp[102] += dp[i] * (100 - i).quo(100) * P1_3
        else
            ndp[i + q] += dp[i] * (100 - i).quo(100) * P1_3
            ndp[101] += dp[i] * (100 - i).quo(100) * P1_3
            ndp[102] += dp[i] * (100 - i).quo(100) * P1_3
        end
        
        # use
        if i - q < 0
            ndp[0] += dp[i] * i.quo(100) * P1_2
            ndp[101] += dp[i] * i.quo(100) * P1_2
        else
            ndp[i - q] += dp[i] * i.quo(100) * P1_2
            ndp[101] += dp[i] * i.quo(100) * P1_2
        end
    end
    dp = ndp
end

puts dp[101].to_f