#include <bits/stdc++.h>
#define int long long
#define IOS ios::sync_with_stdio(false), cin.tie(0), cout.tie(0)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int INF = 0xffffffff;
const int MOD = 1e9 + 7;
const double PI = acos(-1);
int a, b, c, d;
int dp[30][30];
signed main() {
	IOS;
	memset(dp, 0, sizeof(dp));
	cin >> a >> b >> c >> d;
	dp[1][0] = 1, dp[0][1] = 1;
	for (int i = 1; i <= a+1; ++i) {
		for (int j = 1; j <= b+1; ++j) {
			dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
			if ((i == c - 2 && j == d + 1) || (i == c - 2 && j == d - 1) || (i == c + 2 && j == d - 1) || (i == c + 2 && j == d + 1) || (i == c && j == d))
				dp[i][j] = 0;
			else if ((i == c - 1 && j == d + 2) || (i == c - 1 && j == d - 2) || (i == c + 1 && j == d - 2) || (i == c + 1 && j == d + 2))
				dp[i][j] = 0;
		}
	}
	cout << dp[a][b];
	return 0;
}