#include <bits/stdc++.h>
using namespace std;
long long dp[25][25];
int n,m,x,y;
int main(){
	memset(dp,0x3f3f3f3f,sizeof(dp));
	cin>>n>>m>>x>>y;
	for(int i=0;i<=m;++i){
		dp[0][i]=1;
	}
	for(int i=0;i<=n;++i){
		dp[i][0]=1;
	}//初始化 
	dp[x][y]=0;
	if(x+1<=m&&y+2<=n)dp[x+1][y+2]=0;
	if(x+2<=m&&y+1<=n)dp[x+2][y+1]=0;
	if(x+2<=m&&y-1>=0)dp[x+2][y-1]=0;
	if(x+1<=m&&y-2>=0)dp[x+1][y-2]=0;
	if(x-1>=0&&y-2>=0)dp[x-1][y-2]=0;
	if(x-2>=0&&y-1>=0)dp[x-2][y-1]=0;
	if(x-2>=0&&y+1<=n)dp[x-2][y+1]=0;
	if(x-1>=0&&y+2<=n)dp[x-1][y+2]=0;
	
	for(int i=1;i<=n;++i){
		for(int j=1;j<=m;++j){
			if(dp[i][j]>0){
				dp[i][j]=dp[i-1][j]+dp[i][j-1];
			}
		}
	}
	
	/*for(int i=0;i<=n;++i){
		for(int j=0;j<=m;++j){
			cout<<dp[i][j]<<" ";
		}
		cout<<endl;//
	}*/
	cout<<dp[n][m];
	return 0;
}