#include<stdio.h>
int a[100][100];
int check(int,int,int,int);
int check(int x,int y,int mx,int my)
{
	if(x==mx&&y==my) return 1;	
	if(x==mx+2&&y==my+1) return 1;
	if(x==mx+2&&y==my-1) return 1;
	if(x==mx-2&&y==my+1) return 1;
	if(x==mx-2&&y==my-1) return 1;
	if(x==mx+1&&y==my+2) return 1;
	if(x==mx+1&&y==my-2) return 1;
	if(x==mx-1&&y==my-2) return 1;
	if(x==mx-1&&y==my+2) return 1;
	return 0;
}
int main()
{
	int mx,my,x,y,zx,zy;
	int i,j;
	scanf("%d%d%d%d",&zx,&zy,&mx,&my);
	a[0][0]=1;
	for(i=0;i<=zx;i++)
	{
		for(j=0;j<=zy;j++)
		{
			if(i==0&&j==0) continue; 
			a[i][j]=a[i-1][j]+a[i][j-1];
			if(check(i,j,mx,my))
			{
				a[i][j]=0;
			}
		}
	}
	printf("%d",a[zx][zy]);
	return 0;
}