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

val () =
    let
        val a = readLargeInt ()
        val b = readLargeInt ()
        val c = readLargeInt ()
        val d = readLargeInt ()

        val ans = if a = c orelse b = d orelse abs (a - c) + abs (b - d) <= 3
                  then 1
                  else 2
    in
        print (LargeInt.toString ans ^ "\n")
    end