gets.to_i.times{
    s = gets.chomp
    s.reverse =~ /R(.*?)G/
    if s[-1] != 'R' || $1.to_s.include?('W')
        puts "impossible"
    else
    loop{
                s.gsub!(/WG(.*?)R/){$1}
                if $&.nil?
                    break
                end
                }
                if s.include?('R')
                    puts "impossible"
                else
                    puts "possible"
                end
    end
    }