T=int(input())


for i in range(T):
  w=g=r=0
  t=True
  S=input()
  for i,j in enumerate(S):
    if not w>=g>=r:
      print("impossible")
      t=False
      break
    if j=="W":
      w+=1
      la=i
    if j=="G":
      g+=1
      l=i
    if j=="R":
      r+=1
  if t:
    if g==r and g>0 and l>la:
      print("possible")
    else:
      print("impossible")