for _ in[0]*input():
	s=raw_input()
	g=r=p=0
	for c in s[::-1]:
		if c=="R":
			r+=1
		elif c=="G":
			g+=1
			if g>r:
				break
		elif c=="W":
			if r>0 and g==0 and p==0:
				break
			if g>0 and r>0:
				r-=1
				g-=1
				p+=1
		#print r,g
	if g==r and r==0 and s[-1]!="W":
		print"possible"
	else:
		print"impossible"