class Calc0154
  def initialize(args)
    args = args.map { |l| l.chomp.split(/\s+/) }
    @n = args.shift.first.to_i
    @ss = args.map(&:first)
  end

  def calc(s)
    ws = s.count('W')
    gs = s.count('G')
    rs = s.count('R')
    !s.end_with?('W') &&
      ws >= 1 && gs >= 1 && rs >= 1 &&
      s.rindex('W') < s.rindex('G') &&
      gs == rs && check_times(s)
  end

  def check_times(s)
    ws = gs = rs = 0
    s.split(//).each do |c|
      ws += 1 if c == 'W'
      gs += 1 if c == 'G'
      rs += 1 if c == 'R'
      return false if gs > ws || rs > gs
    end
    true
  end

  def run
    @ss.map { |s| calc(s) }.map { |r| r ? 'possible' : 'impossible' }.join("\n")
  end
end

puts Calc0154.new(STDIN.readlines).run if __FILE__ == $0