#include<bits/stdc++.h> 
using namespace std;

int main() {
	int n, m, x, y;
	cin >> n >> m >> x >> y;
	int a[30][30] = { 0 };
	a[1][1] = 1;
	x++; y++;
	for (int i = 1; i <= n+1; i++) {
		for (int j = 1; j <= m+1; j++) {
			if (i == 1 && j == 1)
				continue;
			if (i == x && j == y)
				continue;
			if (i == x - 2 && j == y - 1)
				continue;
			if (i == x - 1 && j == y - 2)
				continue;
			if (i == x - 2 && j == y + 1)
				continue;
			if (i == x - 1 && j == y + 2)
				continue;
			if (i == x + 2 && j == y - 1)
				continue;
			if (i == x + 1 && j == y - 2)
				continue;
			if (i == x + 2 && j == y + 1)
				continue;
			if (i == x + 1 && j == y + 2)
				continue;
			a[i][j] = a[i-1][j] + a[i][j-1];
		}
	}
	cout << a[n+1][m+1];
	return 0;
}