#include<iostream>

using namespace std;

int max(int a, int b)
{
	if (a > b)
		return a;
	else
		return b;
}

int main()
{
	int m, n, a, b;
	cin >> m >> n >> a >> b;
	cout << endl;

	long long arr[25][25];

	
	for (int i = 0; i < m + 1; i++)
	{
		for (int j = 0; j < n + 1; j++)
		{
			arr[i][j] = 1;
		}

	}
	
	arr[a][b] = 0;
	for (int i = -3; i < 4; i++)
	{
		for (int j = -3; j < 4; j++)
		{
			int n1 = abs(i), n2 = abs(j);
			if ((n1 + n2 == 3)&&(max(n1, n2) == 2)&&(max(a+i,b+j)>-1))
				arr[a + i][b + j] = 0;
		}
	}
	
	for (int i = 1; i < m + 1; i++)
	{
		for (int j = 1; j < n + 1; j++)
		{
			if (arr[i][j] != 0)
			{
				if (i > 0 && j > 0)
					arr[i][j] = arr[i - 1][j] + arr[i][j - 1];
				else
					arr[i][j] = 1;
			}
		}

	}
	cout << arr[m][n];
}