gets.to_i.times{
    s = gets.chomp
    if s.count('G') != s.count('R')
        puts "impossible"
    else
        s.reverse =~ /R(.*?)G/
        if s.rindex('R') != s.length - 1 || $1 != ''
            puts "impossible"
        else
            if s.gsub(/G(.*?)R/){$1}.include?('R')
                puts "impossible"
            else
                puts "possible"
            end
        end
    end
    }