#include<bits/stdc++.h>
using namespace std;
int m,n,a,b;
long long ma[22][22],map1[30][30];
void bj(int x,int y)
{
	map1[x][y]=1;
	map1[x-1][y-2]=1;
	map1[x-2][y-1]=1;
	map1[x+1][y-2]=1;
	map1[x-2][y+1]=1;
	map1[x-1][y+2]=1;
	map1[x+2][y-1]=1;
	map1[x+1][y+2]=1;
	map1[x+2][y+1]=1;//标记马的位置 
	
}
int main()
{
	cin>>n>>m>>a>>b;
	bj(a,b);
	ma[1][0]=1;
	for(int i=1;i<=n+1;i++)
	{
		for(int j=1;j<=m+1;j++)
		{
			ma[i][j]=ma[i-1][j]+ma[i][j-1];
			if(map1[i-1][j-1]) ma[i][j]=0;
		}
	}
	cout<<ma[n+1][m+1];
	return 0;
 }