using System.Numerics;

public class Program
{
    public static void Main()
    {

        //BigInteger num = BigInteger.Parse(Console.ReadLine() ?? string.Empty);
        //int num = int.Parse(Console.ReadLine() ?? string.Empty);
        string[] moji = (Console.ReadLine() ?? string.Empty).Trim().Split(' ');
        //string str = Console.ReadLine() ?? string.Empty;


        BigInteger a = BigInteger.Parse(moji[0]);
        BigInteger b = BigInteger.Parse(moji[1]);
        BigInteger c = BigInteger.Parse(moji[2]);
        BigInteger d = BigInteger.Parse(moji[3]);


        if (a == c || b == d)
        {
            Console.WriteLine(1);
        }
        else if(a+2<c||b+2<d||a-2>c||b-2>d)
        {
            Console.WriteLine(2);
        }
        else 
        {
            if(a+2==c||a-2==2)
            {
                if(b+2==d||b-2==d)
                {
                    Console.WriteLine(2);
                }
                else
                {
                    Console.WriteLine(1);
                }
            }
            else if(b+2==d||b-2==d)
            {
                if(a+2==c||a-2==c)
                {
                    Console.WriteLine(2);
                }
                else
                {
                    Console.WriteLine(1);
                }
            }
            else
            {
                Console.WriteLine(1);
            }
               
        }
            //else if (a - 2 <= c && c <= a && b - 2 <= d && d <= b  || a - 2 <= c && c <= a && b + 2 >= d && d >= b ||
            //    a + 2 >= c && c >= a && b - 2 <= d && d <= b  || a + 2 >= c && c >= a && b + 2 >= d && d >= b )
            //{
            //    Console.WriteLine(1);
            //}
        //else
        //{
        //    Console.WriteLine(2);
        //}
        //a!=c&&b!= d==console.writeline(2);
        //&&a-2 != c&& b-2!=d
        //&&a-2!=c&&b+2!=d
        //&&a +2!=c&&b-2!=d
        //&&a+2!=c&&b+2!=d
    }
}