{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE BangPatterns #-}

import Control.Applicative
import Control.Monad
import Control.Arrow
import Data.List
import Data.Maybe
import Data.Char
import qualified Data.ByteString.Char8 as B
import Text.Printf

readInt = ( readLn :: IO Int )
readInts = map ( read :: String -> Int ) . words <$> getLine

getList = map ( fst . fromJust . B.readInt ) . B.words <$> B.getLine

which a b f = if f then a else b
mp [ a, b ] = ( a, b )

main = getLine >> getContents >>= mapM_ putStrLn . map ( which "possible" "impossible"  . f 0 0 0 . reverse ) . lines

f 0 0 _ [] = True
f r g w ('R':s) = f ( r + 1 ) g w s
f 0 _ _ ('G':s) = False
f r g w ('G':s) = f ( r - 1 ) ( g + 1 ) w s
f r 0 0 ('W':s) = False
f r 0 w ('W':s) = f r 0 w s
f r g w ('W':s) = f r ( g - 1 ) ( w + 1 ) s
f _ _ _ _ = False