#include<bits/stdc++.h>
using namespace std;
unsigned long long dp[25][25];
bool f[25][25];
const int dx[9]={-2,-2,-1,1,2,2,1,-1,0},dy[9]={-1,1,2,2,1,-1,-2,-2,0};
int main()
{
	int n,m,x,y;
	cin>>n>>m>>x>>y;
	for (int i=0;i<=n;++i) dp[i][0]=1;
	for (int i=0;i<=m;++i) dp[0][i]=1;
	for (int i=0;i<9;++i)
	{
		int nx=x+dx[i],ny=y+dy[i];
		if (nx>=0&&nx<=n&&ny>=0&&ny<=m) {dp[nx][ny]=0;f[nx][ny]=true;}
	}
	for (int i=1;i<=n;++i)
		for (int j=1;j<=m;++j)
			if (!f[i][j]) dp[i][j]=dp[i-1][j]+dp[i][j-1];
	cout<<dp[n][m];
	return 0;
}