fun readLargeInt () =
    valOf (TextIO.scanStream (LargeInt.scan StringCvt.DEC) TextIO.stdIn)


val () =
    let
        val x = readLargeInt ()
        val y = readLargeInt ()
        val x2 = readLargeInt ()
        val y2 = readLargeInt ()

        val ans = if x = y andalso x2 = y2 andalso x2 < x then x + 1
                  else LargeInt.max (x, y)
    in
        print (LargeInt.toString ans ^ "\n")
    end