import Control.Monad
import Data.Monoid
import Data.List
 
getInt = read <$> getLine :: IO Int
getInts = map read . words <$> getLine :: IO [Int]
 
f s t 0 
    | slen < tlen = Nothing
    | any (\(x, y) -> x/='?' && x/=y) pairs = Nothing
    | otherwise = Just (t ++ (map g $ drop tlen s))
    where
        slen = length s
        tlen = length t
        pairs = zip s t
        g c = if c=='?' then 'a' else c
f [] t n = Nothing
f (c:s) t n = (c':) <$> f s t (n-1)
    where c' = if c=='?' then 'a' else c
    
    
main = do
    s' <- getLine
    t <- getLine
    putStrLn $ maybe "UNRESTORABLE" id $ getLast $ foldMap Last $ map (\n -> f s' t n) [0..(length s')]
    