using static System.Math;
using System;

public class Hello
{
    public static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var x = int.Parse(line[0]);
        var y = int.Parse(line[1]);
        line = Console.ReadLine().Trim().Split(' ');
        var x2 = int.Parse(line[0]);
        var y2 = int.Parse(line[1]);
        var xymin = Max(x, y);
        var nx = x - xymin;
        var ny = y - xymin;
        Console.WriteLine(nx + ny + xymin);
    }
}