n=int(input())
a="impossible"
for i in range(n):
	c=-2
	s=input()
	m=len(s)
	if m>2 and s[0]!='G':
		for i in range(1,m):
			t=s[-i:]
			if 'W' in t: break
			if 'G' in t and 'R' in t: c+=2; break
		s=s.replace('W','')
		for x in s:
			if x=='G':c+=1
			else:c-=1
			if c<0: break
	print(a[(c==0)*2:])