#include<iostream>
using namespace std;
long long map[22][22]={0};
bool b[22][22]={0};
int n,m,x,y;
int main()
{
	map[1][1]=1;
	cin>>n>>m>>x>>y;
	n++;m++;x++;y++;
	b[x][y]=1;
	b[x-1][y-2]=1;
	b[x-1][y+2]=1;
	b[x+1][y-2]=1;
	b[x+1][y+2]=1;
	b[x-2][y+1]=1;
	b[x-2][y-1]=1;
	b[x+2][y+1]=1;
	b[x+2][y-1]=1;
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=m;j++)
		{
			if(i==1&&j==1)continue;
			if(b[i][j]==0)
				map[i][j]=map[i][j-1]+map[i-1][j];
		}
	}
	cout<<map[n][m];
	return 0;
 }