using System;

class Program
{
    static void Main()
    {
        long x1 = long.Parse(Console.ReadLine());
        long y1 = long.Parse(Console.ReadLine());
        long x2 = long.Parse(Console.ReadLine());
        long y2 = long.Parse(Console.ReadLine());

        long dx = Math.Abs(x2 - x1);
        long dy = Math.Abs(y2 - y1);

        if (dx + dy <= 2 || dx == 0 || dy == 0)
        {
            Console.WriteLine(1);
        }
        else if ((dx + dy <= 3) || (dx == dy) || (dx + dy) % 2 == 0)
        {
            Console.WriteLine(2);
        }
        else
        {
            Console.WriteLine(3);
        }
    }
}