import Control.Monad

go w x g ('W':cs)           = go (w+1) x g cs
go w x g ('G':cs) | w+x > 0 = go 0 (w+x-1) (g+1) cs
go w x g ('R':cs) | g > 0   = go w x (g-1) cs
go 0 _ 0 []                 = "possible"
go _ _ _ _                  = "impossible"

main = do
  t <- readLn
  ss <- replicateM t getLine
  mapM_ (putStrLn . go 0 0 0) ss