fun readStr () =
    let
        fun scan reader stream = SOME (StringCvt.splitl (not o Char.isSpace) reader (StringCvt.skipWS reader stream))
    in
        valOf (TextIO.scanStream scan TextIO.stdIn)
    end
      

fun findAns s =
    let 
        fun findAnsAux [] = []
          | findAnsAux [x] = [x]
          | findAnsAux (h1 :: h2 :: tl) = 
            if h1 = h2 then h1 :: findAnsAux(tl)
            else h1 :: findAnsAux(h2 :: tl)
    in
        String.implode (findAnsAux (String.explode s))
    end


val () =
    let
        val s = readStr ()
                        
        val ans = findAns s
    in
        print (ans ^ "\n")
    end