using System;

namespace malanguohe { class Program { static void Main(string[] args) {

        int[,] map = new int[25, 25];
        int[,] a = new int[25, 25];
        a[1, 0] = 1;


        void m(int mmx, int mmy)
        {
            
            map[mmx + 2, mmy + 1] = 1;
            map[mmx + 1, mmy + 2] = 1;
            map[mmx - 1, mmy + 2] = 1;
            map[mmx - 2, mmy + 1] = 1;
            map[mmx - 2, mmy - 1] = 1;
            map[mmx - 1, mmy - 2] = 1;
            map[mmx + 1, mmy - 2] = 1;
            map[mmx + 2, mmy - 1] = 1;
            map[mmx, mmy] = 1;

        }


        string[] s = Console.ReadLine().Split();
        
        int x = int.Parse(s[0]);
        int y = int.Parse(s[1]);
         
        int mx = int.Parse(s[2]);
        int my = int.Parse(s[3]);

       


        m(mx, my);
        for(int i=1;i<=x+1;i++)
            for(int j = 1;j <=y+1;j++)
            {
                a[i, j] = a[i - 1, j] + a[i, j - 1];
               if(map[i-1,j-1]==1)
                {
                    a[i, j] = 0;
                }
                

            }
           
        }
        Console.WriteLine(a[x+1, y+1]);

       

       



        Console.ReadLine();
    }
}

}