#include <bits/stdc++.h>
using namespace std;
long long dp[2010][2010];
int main(){
	int n,m,x,y;
	cin>>n>>m>>x>>y;
	dp[x][y]=-1;
	dp[x-2][y-1]=-1;
	dp[x-2][y+1]=-1;
	dp[x-1][y-2]=-1;
	dp[x-1][y+2]=-1;
	dp[x+1][y+2]=-1;
	dp[x+1][y-2]=-1;
	dp[x+2][y-1]=-1;
	dp[x+2][y+1]=-1;
	dp[0][0]=1;
	for(int i=1;i<=n;i++){
		if(dp[i][0]==-1)dp[i][0]=0;
		else dp[i][0]=dp[i-1][0];
	}
	for(int i=1;i<=m;i++){
		if(dp[0][i]==-1)dp[0][i]=0;
		else dp[0][i]=dp[0][i-1];
	}
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			if(dp[i][j]==-1)dp[i][j]=0;
			else dp[i][j]=dp[i-1][j]+dp[i][j-1];
		}
	}
	cout<<dp[n][m];
    return 0;
}