#include <iostream>
#include<bits/stdc++.h>
using namespace std; 
int main() {
	int room[25][25]={0};
	int x,y,x1,y1;
	cin>>x>>y>>x1>>y1;
	room[0][0]=1;
	room[x1][y1]=-1;
	if(x1>0&&y1>1)	room[x1-1][y1-2]=-1;
	if(x1<20&&y1>1)	room[x1+1][y1-2]=-1;
	if(x1<19&&y1>0)	room[x1+2][y1-1]=-1;
	if(x1<19&&y1>0)	room[x1+2][y1+1]=-1;
	if(x1<20&&y1<19) room[x1+1][y1+2]=-1;
	if(x1>0&&y1<19) room[x1-1][y1+2]=-1;
	if(x1>1&&y1<20) room[x1-2][y1+1]=-1;
	if(x1>1&&y1>0) room[x1-2][y1-1]=-1;
	for(int i=0;i<=x;i++)
	{
		for(int j=0;j<=y;j++)
		{
			if(room[i][j]==-1)
			{
				room[i][j]=0;
				continue;
			}
			if(i==0&&j>0)
			{
				room[i][j]=room[i][j-1];
			}
			else if(j==0&&i>0)
			{
				room[i][j]=room[i-1][j];
			}
			else if(j!=0&&i!=0)
			room[i][j]=room[i][j-1]+room[i-1][j];
		}
	}
	cout<<room[x][y];
	return 0;
}
`