using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Problem154
{
    class Program
    {
        static void Main(string[] args)
        {
            int T = int.Parse(Console.ReadLine());

            string[] S = new string[T];
            for (int i = 0; i < T; i++)
                S[i] = Console.ReadLine();

            for(int i = 0; i < T; i++)
            {
                int wcount = 0;
                int gcount = 0;
                int wright = 0;
                int gright = 0;
                for(int j = 0; j < S[i].Length; j++)
                {
                    char s = S[i][j];
                    if (s == 'W')
                    {
                        wcount++;
                        wright = j;
                    }
                    else if(s == 'G')
                    {
                        gright = j;
                        if(--wcount < 0)
                        {
                            Console.WriteLine("impossible");
                            break;
                        }
                        else
                        {
                            gcount++;
                        }
                    }
                    else if(s == 'R')
                    {
                        if(--gcount < 0)
                        {
                            Console.WriteLine("impossible");
                            break;
                        }
                    }
                }

                if (wright >= gright)
                {
                    Console.WriteLine("impossible");
                }
                else
                {
                    if (gcount == 0)
                    {
                        Console.WriteLine("possible");
                    }
                    else if (gcount > 0)
                    {
                        Console.WriteLine("impossible");
                    }
                }
            }

        }
    }
}