#include <bits/stdc++.h>
const int N = 20 + 10;
using namespace std;

int n, m, x, y;

long long f[N][N];
bool g[N][N];
int c[9] = {0, 1, 1, -1, -1, 2, 2, -2, -2},
    d[9] = {0, -2, 2, -2, 2, 1, -1, -1, 1};

int main()
{
	cin >> n >> m >> x >> y;
	memset(g, 1, sizeof(g));
	g[x][y] = 0;
	for (int i = 1; i <= 8; ++ i)
	{
		if (x + c[i] < 0 || y + d[i] < 0) continue;
		g[x + c[i]][y + d[i]] = false;
	}
	f[0][0] = 1;
	for (int i = 1; i <= m; ++ i)
	{
		if (g[0][i] == 0) break;
		else f[0][i] = f[0][i - 1];
	}
	for (int i = 1; i <= n; ++ i)
	{
		if (g[i][0] == 0) break;
		else f[i][0] = f[i - 1][0];
	}
	for (int i = 1; i <= n; ++ i)
		for (int j = 1; j <= m; ++ j)
			if (g[i][j]) f[i][j] = f[i - 1][j] + f[i][j - 1];
	cout << f[n][m] << endl;
	return 0; 
}