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

int n, m, x, y;
int a[30][30];

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