#include <bits/stdc++.h>
using namespace std;
bool m[21][21]={1};
void ma(int x,int y)
{
	m[x][y]=0;
	m[x+2][y+1]=0;
	m[x+1][y+2]=0;
	m[x-1][y+2]=0;
	m[x-2][y+1]=0;
	m[x-2][y-1]=0;
	m[x-1][y-2]=0;
	m[x+1][y-2]=0;
	m[x+2][y-1]=0;
}
int x,y,mx,my,f[21][21]; 
int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cin>>x>>y>>mx>>my;
	ma(mx,my);
	f[0][0]=1;
	for(int i=0;i<x;i++)
	{
		for(int j=0;j<y;j++)
		{
			if(i==0||j==0)
			{
				f[i][j]=1;
				continue;
			}
			if(m[i][j]) f[i][j]=f[i-1][j]+f[i][j-1];
		}
	}
	cout<<f[x][y];
	return 0;
}