1 import java.util.Scanner;
2
3 public class Main{
4 static int hl[][]=new int[20][20];
5 static int sum=0;
6 static int blx,bly;
7 public static void unreach(int hx,int hy){
8 hl[hx][hy]=hl[hx+1][hy+2]=hl[hx+2][hy+1]=hl[hx+2][hy-1]=hl[hx+1][hy-2]=hl[hx-1][hy-2]
9 =hl[hx-2][hy-1]=hl[hx-2][hy+1]=hl[hx-1][hy+2]=1;
10 }
11 public static void count(int sx,int sy){
12 if(hl[sx][sy]==1||sx>blx||sy>bly){
13 return;
14 }
15 if(sx==blx&&sy==bly){
16 sum++;
17 return;
18 }
19 count(sx+1,sy);
20 count(sx,sy+1);
21 }
22 public static void main(String args[]){
23 Scanner sc=new Scanner(System.in);
24 int bx,by,hx,hy;
25 bx=sc.nextInt();
26 by=sc.nextInt();
27 blx=bx;
28 bly=by;
29 hx=sc.nextInt();
30 hy=sc.nextInt();
31 unreach(hx,hy);
32 count(0,0);
33 System.out.println(sum);
34 }
35 }
