#include<iostream>
#include<cstdio>
using namespace std;	
long long ps[22][22];
bool jd[22][22];
int main()
{
	int a,b,x,y;
	cin>>a>>b>>x>>y;
	jd[x+2][y+2]=1;
	jd[x][y+3]=1;
	jd[x][y+1]=1;
	jd[x+1][y+4]=1;
	jd[x+1][y]=1;
	jd[x+3][y+4]=1;
	jd[x+3][y]=1;
	jd[x+4][y+3]=1;
	jd[x+4][y+1]=1;
	for(int i=2;i<=a+3;i++)
	{
		if(jd[i][2]==0)
		{
		ps[i][2]=1;
		}
		
	}
	for(int i=2;i<=b+2;i++)
	{
		if(jd[2][i]==0)
		{
		ps[2][i]=1;
		}
	}
	
	for(int i=3;i<=a+2;i++)
	{
		for(int j=3;j<=b+2;j++)
		{
			if(jd[i][j]==0)
			{
				ps[i][j]=ps[i-1][j]+ps[i][j-1];
			}
			else
			{ 
			ps[i][j]=0;
			}
		}
	}
	cout<<ps[a+2][b+2];
	return 0;
}