def solve(s)
  last_w = 0
  last_g = 0
  counter = {W: 0, G: 0}
  s.each_char.with_index do |c, i|
    if c == 'W'
      last_w = i
      counter[:W] += 1
    elsif c == 'G'
      if counter[:W] == 0
        return false
      else
        last_g = i
        counter[:W] -= 1
        counter[:G] += 1
      end
    else
      if counter[:G] == 0
        return false
      else
        counter[:G] -= 1
      end
    end
  end
  if last_w > last_g or counter[:G] != 0 or s[-1] != 'R'
    return false
  end
  return true
end

n = gets.to_i

n.times do
  puts solve(gets.chomp) ? 'possible' : 'impossible'
end