gets.to_i.times{
    s = gets.chomp
    g = s.count('G')
    r = s.count('R')
    w = s.count('W')
    if g != r || w < g
        puts "impossible"
    else
        s.reverse =~ /R(.*?)G/
        if s[-1] != 'R' || s[0] != 'W' || $1.include?('W')
            puts "impossible"
        else
            s.delete!('W')
            g.times{
                s.gsub!(/G(.*?)R/){$1}
                }
                if s.include?('R')
                    puts "impossible"
                else
                    puts "possible"
                end
        end
    end
    }