require "set"

class Start
  def main
    _ = input
    puts "? aa"
    s = Set["aa"]

    while true
      x = input.split[1]
      break if x.include?("WIN")
      if x[0] != "a" || s.include?(x)
        _ = input
        break
      end
      t = x[-1] + "a"
      s.add x
      s.add t
      echo "? #{t}"
    end
  end

  protected

  def echo(*x)
    print(*x)
    puts
  end

  def input = gets.chomp
end

Start.new.main