using System; using System.IO; using System.Linq; using System.Collections; using System.Collections.Generic; using System.Numerics; using System.Text; using System.Text.RegularExpressions; using System.Threading.Tasks; using static System.Math; using Int = System.Int64; using Debug = System.Diagnostics.Debug; class P { static void Main() { var a = Console.ReadLine().Split().Select(int.Parse).ToList(); var b = Console.ReadLine().Split().Select(int.Parse).ToList(); Console.WriteLine((a[0] - b[0] + 1) / 2 + (a[1] - b[1] + 1) / 2); } }