def check(S):
	W = 0
	R = 0
	hasW = False
	hasR = False
	hasG = False
	for c in S:
		if c == 'W':
			W += 1
		elif c == 'G':
			W -= 1
		if W < 0: return False
	for c in S[::-1]:
		if c == 'W':
			if not hasG: return False
		elif c == 'G':
			hasG = True
			R -= 1
		else:
			R += 1
		if R < 0: return False
	return R == 0

T = input()
for i in xrange(T):
	S = raw_input()
	if check(S):
		print 'possible'
	else:
		print 'impossible'