import strutils, sequtils, math

let
  xy, x2y2 = stdin.readLine.split.map parseInt
  (x, y) = (xy[0], xy[1])
  (x2, y2) = (x2y2[0], x2y2[1])
var
  offset = 0

if x.abs == y.abs and x2.abs == y2.abs:
  if x.sgn == x2.sgn and y.sgn == y2.sgn:
    offset += 2

echo max(x.abs, y.abs) + offset