#include<bits/stdc++.h>
#define ll long long
using namespace std;
ll x,y,n,m,ans=0;
void dfs(int m1,int m2,int b1,int b2){
	if(b1==n && b2==m) ans++;
	else{
		if((b1+1!=m1 || b2!=m2) && (b1+1!=m1-2 || b2!=m2+1) && (b1+1!=m1-2 || b2!=m2-1) && (b1+1!=m1-1 || b2!=m2-2) && (b1+1!=m1-1 || b2!=m2+2) && (b1+1!=m1+1 || b2!=m2-2) && (b1+1!=m1+1 || b2!=m2+2) && (b1+1!=m1+2 || b2!=m2-1) && (b1+1!=m1+2 || b2!=m2+1)) dfs(m1,m2,b1+1,b2);
		if((b1!=m1 || b2+1!=m2) && (b1!=m1-2 || b2+1!=m2+1) && (b1!=m1-2 || b2+1!=m2-1) && (b1!=m1-1 || b2+1!=m2-2) && (b1!=m1-1 || b2+1!=m2+2) && (b1!=m1+1 || b2+1!=m2-2) && (b1!=m1+1 || b2+1!=m2+2) && (b1!=m1+2 || b2+1!=m2-1) && (b1!=m1+2 || b2+1!=m2+1)) dfs(m1,m2,b1,b2+1);
	}
	cout<<ans;
}
int main(){
	cin>>n>>m>>x>>y;
	dfs(x,y,n,m);
	return 0;
}