WIN = 101
LOSE = 102
C = 20
P = (0 .. 100).map{|v| v.quo(100).to_f }
P1_3 = 1.quo(3).to_f
P1_2 = 1.quo(2).to_f

pp, q = gets.split.map(&:to_i)

dp = Array.new(C + 1){ Array.new(101 + 2, 0.0) }
dp[0][101] = P1_3
dp[0][102] = P1_3
dp[0][pp] = P1_3

C.times do |j|
    [WIN, LOSE].each {|r| dp[j + 1][r] = dp[j][r] }
    (0 .. 100).each do |i|
        # unuse 
        [ [i + q, 100].min, WIN, LOSE].each {|r| dp[j + 1][r] += dp[j][i] * P[100 - i] * P1_3 }
        # use
        [ [i - q, 0].max, WIN, LOSE].each {|r| dp[j + 1][r] += dp[j][i] * P[i] * P1_2 }
    end
end
puts dp[C][101]