T = int(input())
for i in range(T):
	S = input()
	flag = True
	w,g,ww = 0,0,0
	for s in S:
		if s == 'W':
			w += 1
			ww+=1
		elif s == 'G':
			w -= 1
			g += 1
			ww = 0
		else:
			g -= 1
		if g < 0 or w < 0:
				flag = False
	if g > 0 or ww > 0:
		flag = False
	if flag:
		print("possible")
	else:
		print("impossible")