#include<bits/stdc++.h>
//#include<iostream>
//#include<cstring>
//#include<cstdio>
//#include<algorithm>
//#define ll long long
using namespace std;


const int mx[] = {0, -2, -1, 1, 2, 2, 1, -1, -2};
const int my[] = {0, 1, 2, 2, 1, -1, -2, -2, -1};
int x, y, sx, sy;
ll f[40][40];
bool vis[40][40];


int main(){
	scanf("%d%d%d%d", &x, &y, &sx, &sy);
	x += 2;
	y += 2;
	sx += 2;
	sy += 2;
	f[2][1] = 1;
	vis[sx][sy] = 1;
	for(int i = 1; i <= 8; i++){
		vis[sx + mx[i]][sy + my[i]] = 1;
	}
	for(int i = 2; i <= x; i++){
		for(int j = 2; i <= y; j++){
			if(vis[i][j]){
				continue;
			}
			f[i][j] = f[i - 1][j] + f[i][j - 1];
		}
	}
	printf("%lld\n", f[x][y]);
	return 0;
}