a = gets.to_i
p0, p1, p2 = gets.split.map{|s|1.0 - s.to_f / 100}
list = [1.0] * 16
list[0] = 0.0
list[15] = 0.0
next_list = nil
(80 - a).times do
  next_list = list.clone
  (1..14).each do |i|
    next_list[i] = list[i] * (p0 * (1.0 - list[i - 1]) * (1.0 - list[i + 1]) +
                              p1 * (1.0 - list[i - 1]) * list[i + 1]         +
                              p1 * list[i - 1]         * (1.0 - list[i + 1]) +
                              p2 * list[i - 1]         * list[i + 1]         )
  end
  list = next_list
end
puts list.inject{|s, p|s + p} * 2