using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication4 {
    class Program {
        static void Main() {
            int[] a = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
            int[] b = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
            int x = a[0];
            int y = a[1];
           int x1 = b[0];
            int y1 = b[1];
            long[,] f = new long[y, x];
            for(int i = 0; i < y; i++) {
                for(int j = 0; j < x; j++) {
                    if (i == 0) {
                        f[i, j] = j+1;

                    }
                    else if (j == 0) {
                        f[i, j] = i+1;
                    }
                    else if (i == y1 && j == x1) {
                        f[i, j] = long.MaxValue;
                    }
                    else {
                        f[i, j] = Math.Min(f[i - 1, j], f[i, j - 1]) + 1;
                    }

                }
            }
            Console.WriteLine(f[y - 1, x - 1]);
        }
    }
}