#include <bits/stdc++.h>
using namespace std;
int x[8] = {1,1,-1,-1,2,2,-2,-2};
int y[8] = {2,-2,2,-2,1,-1,1,-1};
int vis[21][21],ans = 0;
int bx,by,sx,sy;
int main(){
	cin >> bx >> by >> sx >> sy;
	for(int i = 0;i <= 7;i++){
		if(sx+x[i] >= 0 && sy+y[i] >= 0){
			vis[sx+x[i]][sy+y[i]] = -1;
		}
	}
	vis[sx][sy] = -1;
	if(vis[0][0] != -1)vis[0][0] = 1;
	for(int i = 0;i <= bx;i++){
		for(int j = 0;j <= by;j++){
			if(vis[i][j] != -1&&j > 0 && i > 0){
				vis[i][j] += max(0,vis[i-1][j]) + max(0,vis[i][j-1]);
			}
			else if(vis[i][j] != -1&&j > 0){
				vis[i][j] +=max(0,vis[i][j-1]);
			}
			else vis[i][j] += max(0,vis[i-1][j]);
		}
	}
	if(vis[bx][by] == -1) cout << 0;
	else cout << vis[bx][by];
}