#include<bits/stdc++.h>
using namespace std ;
int a[25][25];
int main() 
{
	int n,m,x,y;
	cin>>n>>m>>x>>y;
	for(int i=0;i<=n;i++)
	{
		for(int j=0;j<=m;j++)
		{
			a[i][j]=1;
		}
	}
	a[x][y]=0;
	if(x+2<=n && y+1<=m) a[x+2][y+1]=0;
	if(x+1<=n && y+2<=m) a[x+1][y+2]=0;
	if(x+2<=n && y-1>=0) a[x+2][y-1]=0;
	if(x+1<=n && y-2>=0) a[x+1][y-2]=0;
	if(x-2>=0 && y+1<=m) a[x-2][y+1]=0;
	if(x-1>=0 && y+2<=m) a[x-1][y+2]=0;
	if(x-2>=0 && y-1>=0) a[x-2][y-1]=0;
	if(x-1>=0 && y-2>=0) a[x-1][y-2]=0; 
	for(int i=0;i<=n;i++)
	{
		for(int j=0;j<=m;j++)
		{
			if(i==0 && j==0) continue;
			if(a[i][j]==0) continue;
			if(i==0)
			{
				a[i][j]=a[i][j-1];
			}
			else if(j==0)
			{
				a[i][j]=a[i-1][j];
			}
			else
			{
				a[i][j]=a[i-1][j]+a[i][j-1];
			}
		}
	}
	cout<<a[n][m];
	return 0 ;
}

/**************************************************************
	Problem: 1224
	User: chenkexin
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2076 kb
****************************************************************/