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

        
fun findAns l s k =
    let
        fun findAnsAux _ [] _ bestIndex = bestIndex
          | findAnsAux index (h::tl) bestVal bestIndex = 
            if abs (h - s) < bestVal
            then findAnsAux (index + 1) tl (abs (h - s)) index
            else findAnsAux (index + 1) tl bestVal bestIndex
    
        val res = findAnsAux 1 l (k + 1) 1000
    in
        if res = 1000 then "Unlucky!"
        else Int.toString res
    end


val () =
    let
        val n = readInt ()
        val s = readInt ()
        val k = readInt ()
        val a_s = List.tabulate (n, fn _ => readInt ())

        val ans = findAns a_s s k
    in
        print (ans ^ "\n")
    end