let s' = read_line ()
let t = read_line ()
let n, m = String.(length s', length t)
let f _ = print_endline "UNRESTORABLE"; exit 0
let _ = if n < m then f (); print_endline @@ String.init n (fun i -> if i < n - m then if s'.[i] = '?' then 'a' else s'.[i] else if s'.[i] = '?' then t.[i - n + m] else if s'.[i] <> t.[i - n + m] then f () else t.[i - n + m])