ws = 0
gs = 0

gets.to_i.times do
  possible = true

  gets.chomp.chars.each do |c|
    case c
    when "W"
      ws += 1
    when "G"
      if ws <= 0
        possible = false
        break
      end
      ws -= 1
      gs += 1
    when "R"
      if gs <= 0
        possible = false
        break
      end
      gs -= 1
    end
  end

  if possible && gs.zero?
    puts "possible"
  else
    puts "impossible"
  end
end