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 == y and x2 == y2:
  if x.sgn == x2.sgn and y.sgn == y2.sgn:
    if x > x2:
      offset += 1

echo max(x, y) + offset