n=int(input())
a,r,g,w="impossible",'R','G','W'
for i in range(n):
	l=[]
	c=0
	for x in input()[::-1]:
		if x==r: l.append(1)
		elif x==g and 1 in l: l[l.index(1)]=2
		elif x==w and 2 in l: l[l.index(2)]=3
		elif x==w and 3 in l: continue
		else: c=1; break
	if len(l)<1: c=1
	elif min(l)<3: c=1
	print(a[(c<1)*2:])