#!/usr/bin/python
# -*- coding: utf-8 -*-

# roiti46 さんのをカンニング

T = input()
for t in range(T):
    inp = raw_input()
    w = last = 0
    needG = False
    # last: 要終電本数
    # needG: 要緑 t/f
    
    for s in inp: #緑より多く赤 or 白より多く緑 はだめ
        if s == 'G':
            last += 1
            w -= 1
            needG = False
        elif s == 'R':
            last -= 1
        else: #s == 'W'
            w += 1
            needG = True
        
        if last < 0 or w < 0: 
            print 'impossible'
            break
    
    else:
        if last == 0 and needG == False: 
            print 'possible'
        else:
            print 'impossible'