#include <iostream>
using namespace std;
int a[25][25],b[25][25],Bx,By;
int main ()
{
	int Mx,My,i,j;
	cin>>Bx>>By>>Mx>>My;
	for (i=0;i<=Bx;i++)
	{
		for (j=0;j<=By;j++)
		{
			a[i][j]=0;
			b[i][j]=0;
		}
	}
	b[Mx][My]=-1;
	b[Mx+1][My+2]=-1;
	b[Mx+2][My+1]=-1;
	b[Mx+2][My-1]=-1;
	b[Mx+1][My-2]=-1;
	b[Mx-1][My-2]=-1;
	b[Mx-2][My-1]=-1;
	b[Mx-2][My+1]=-1;
	b[Mx-1][My+2]=-1;
	for (i=0;i<=Bx;i++)
	{
		for (j=0;j<=By;j++)
		{
			a[i][j]=a[i-1][j]+a[i][j-1];
			a[0][0]=1;
			if (b[i][j]==-1)
			   a[i][j]=0;
		}
	}
	cout<<a[Bx][By];
	return 0;
}