#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>

using namespace std;
int n, m;
int a, b; // a b代表马的位置
int x[] = {2,1,-1,-2,-2,-1,1,2,0 };
int y[] = {-1,-2,-2,-1,1,2,2,1,0 };
// 马的位置 
const int N = 40;
int v[N][N];
long long q[N][N];

int main()
{
	cin >> n >> m >> a >> b;
	for (int i = 0; i < 9; i++)
	{
		if (a + x[i] >= 0 && b + y[i] >= 0 && a + x[i] <= n && b + y[i] <= m) v[a + x[i]][b + y[i]] = 1; // 标记马的位置 
	}
	for (int i = 0; i <= n; i++)
	{
		for (int j = 0; j <= m; j++)
		{
			if (!v[i][j])
				if (i == 0 || j == 0)
				{
					q[i][j] = 1;
 				}
				else
				{
					q[i][j] = q[i - 1][j] + q[i][j - 1];
				}
		}
	}

	cout << q[n][m] << endl;
	return 0;
}