import sys
input=lambda: sys.stdin.readline().rstrip()
t=int(input())
for _ in range(t):
  S=input()[::-1]
  w,g,r=0,0,0
  chk=True
  for s in S:
    if s=="W":
      if g==0:
        chk=False
      else:
        w+=1
    elif s=="G":
      if r==0:
        chk=False
      else:
        r-=1
        g+=1
    else:
      r+=1
  if r>0 or w<g:
    chk=False
  print("possible" if chk else "impossible")