#include <bits/stdc++.h>
using namespace std;
int a,b,n,m,cnt[20][20],dy[8]={-2,-1,1,2,2,1,-1,-2},dx[8]={-1,-2,-2,-1,1,2,2,1};
int main()
{
	cin >> a >> b >> n >> m;
	for (int i=0;i<=a;i++)
		for (int j=0;j<=b;j++)
			cnt[i][j]=1;
	cnt[n][m]=0;
	for (int i=1;i<8;i++)
		if (n+dx[i]<=a&&m+dy[i]<=b&&n+dx[i]>=0&&m+dy[i]>=0)
			cnt[n+dx[i]][m+dy[i]]=0;
	for (int i=1;i<=a;i++)
		for (int j=1;j<=b;j++)
			if (cnt[i][j]!=0)
				cnt[i][j]=cnt[i-1][j]+cnt[i][j-1];
	/*for (int i=0;i<=a;i++)
	{
		for (int j=0;j<=b;j++)
			cout << cnt[i][j] << " ";
		cout << endl;
	}*/
	cout << cnt[a][b];
}