P_0, Q = gets.split.map(&:to_i)

dp = Array.new(111) { Array.new(101, 0.0) }
dp[0][P_0] = ans = 1 / 3.0

110.times do |i|
  0.upto(100) do |j|
    next if dp[i][j] == 0

    ans += dp[i][j] * j / 100.0 * 0.5
    ans += dp[i][j] * (1.0 - j / 100.0) * (1 / 3.0)
    p_n = j + Q
    p_n = 100 if p_n > 100
    p_p = j - Q
    p_p = 0 if p_p < 0
    dp[i + 1][p_n] += dp[i][j] * (1.0 - j / 100.0) * (1 / 3.0)
    dp[i + 1][p_p] += dp[i][j] * (j / 100.0) * 0.5
  end
end

puts ans.round(12)