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


fun intString n =
    if 0 <= n
    then Int.toString n
    else "-" ^ Int.toString (abs n)


val () =
    let
        val n = readInt ()
        val w = readInt ()
        val vw_s = List.tabulate (n, fn _ => (readInt (), readInt()))

        val ans = List.foldl
                      (fn ((v, weight), acc) =>
                          if weight <= w then Int.max(acc, v)
                          else acc)
                      (~1)
                      vw_s
    in
        print (intString ans ^ "\n")
    end