fun readInt () =
    valOf (TextIO.scanStream (Int.scan StringCvt.DEC) TextIO.stdIn)


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


val () =
    let
        val n = readInt ()
        val s_s = List.tabulate (n, fn _ => readStr ())
        
        val ans = List.foldl (fn (acc, s) => s ^ acc) "" s_s
    in
        print (ans ^ "\n")  
    end