#include<bits/stdc++.h>
using namespace std;
int sum,n,m,x,y;
void dfs( int a , int b ){
	if( a == n && b == m ){
		sum++;
		return;
	}
	if( a > x || b > y ){
		return;
	}
	if( a == x && b == y )return;
	if( a == x + 1 && b == y - 2)return;
	if( a == x + 1 && b == y + 2)return;
	if( a == x + 2 && b == y + 1)return;
	if( a == x + 2 && b == y - 1)return;
	if( a == x - 1 && b == y + 2)return;
	if( a == x - 1 && b == y - 2)return;
	if( a == x - 2 && b == y + 1)return;
	if( a == x - 2 && b == y - 1)return;
	dfs( a,b+1 );
	dfs( a+1,b );
}
int main(){
	cin >> n >> m;
	cin >> x >> y;
	dfs( 0,0 );
	cout << sum;
}