#!/usr/bin/env python
#coding:utf8


def read():
    return raw_input()


def work(s):
    chList = "WGR"

    val = [0, 0, 0]
    for ch in s:
        val[chList.find(ch)] += 1
        if not (val[0] >= val[1] >= val[2]):
            print "impossible"
            return

    print "possible" if val[0] >= val[1] and val[1] == val[2] and val[2] > 0 else "impossible"


if __name__ == "__main__":
    for i in range(input()):
        work(read())