#include <iostream>
using namespace std;
int board[25][25];
int main()
{
	int n, m, cx, cy;
	cin >> n >> m >> cx >> cy;
	for (int i = 0;i <= m;i++)
	{
		board[0][i] = 1;
	}
	for (int i = 0;i <= n;i++)
	{
		board[i][0] = 1; 
	}
	board[cx][cy] = -1;
	board[cx-1][cy-2] = -1;
	board[cx-2][cy-1] = -1;
	board[cx-1][cy+2] = -1;
	board[cx-2][cy+1] = -1;
	board[cx+1][cy-2] = -1;
	board[cx+2][cy-1] = -1;
	board[cx+1][cy+2] = -1;
	board[cx+2][cy+1] = -1;
	for (int i = 1;i <= n;i++)
	{
		for (int j = 1;j <= m;j++)
		{
			if (board[i][j] == -1)
			{
				continue;
			}
			board[i][j] = board[i][j-1] + board[i-1][j];
			if (board[i][j-1] == -1)
			{
				board[i][j] += 1;
			}
			if (board[i-1][j] == -1)
			{
				board[i][j] += 1;
			}
		}
	}
	cout << board[n][m] << endl;
 }