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

fun realString n =
    if 0.0 <= n
    then Real.toString n
    else "-" ^ Real.toString (Real.abs n)

fun insertionSort l =
    let
        fun insert x [] = [x]
          | insert x (y::ys) = if x <= y then x::y::ys
                               else y::(insert x ys)
    in
        foldl (fn (x, acc) => insert x acc) [] l
    end

val () =
    let
        val n = readInt ()
        val a_s = List.tabulate (n, fn _ => readInt ())
        fun findMedian l =
            let
                val sorted = insertionSort l
                val i = length l div 2
            in
                if length l mod 2 = 0
                then (Real.fromInt (List.nth(sorted, (i - 1)) + List.nth(sorted, i) )) / 2.0
                else Real.fromInt (List.nth(sorted, i))
            end

        val ans = findMedian a_s
    in
        print (realString ans)
    end