#include<bits/stdc++.h>
using namespace std;
bool ma[30][30];
int cnt[30][30];
int main(){
	int n,m,x,y;
	cin>>m>>n>>x>>y;
	++m;++n;++x;++y;
	++m;++n;++x;++y;
	for(int i=2;i<=m;++i){
		for(int j=2;j<=n;++j){
			cnt[i][j]=1;
		}
	}
	ma[x-2][y+1]=1;
	ma[x-2][y-1]=1;
	ma[x+2][y+1]=1;
	ma[x+2][y-1]=1;
	ma[x-1][y+2]=1;
	ma[x-1][y-2]=1;
	ma[x+1][y+2]=1;
	ma[x+1][y-2]=1;
	ma[x][y]=1;
	cnt[x-2][y+1]=0;
	cnt[x-2][y-1]=0;
	cnt[x+2][y+1]=0;
	cnt[x+2][y-1]=0;
	cnt[x-1][y+2]=0;
	cnt[x-1][y-2]=0;
	cnt[x+1][y+2]=0;
	cnt[x+1][y-2]=0;
	cnt[x][y]=0;
	for(int i=3;i<=m;++i){
		for(int j=3;j<=n;++j){
			if(!ma[i][j]){
				cnt[i][j]=cnt[i-1][j]+cnt[i][j-1];
			}
			else{
				continue;
			}
		}
	}
	cout<<cnt[m][n];
	return 0;
}