#include <bits/stdc++.h>
using namespace std;
int n,m,a,b,xx[15],yy[15];
long long jieguo[25][25];
int in(int x,int y)
{
	for (int i = 0;i < 9;i ++)
	if (xx[i] == x && yy[i] == y)
	return 1;
	
	return 0;
}
int jisuan(int x,int y)
{
	if (x == n && y == m)
	return 1;
	if (jieguo[x][y] != 0)
	return jieguo[x][y];
	if (in(x,y))
	return 0;
	if (x > n || y > m)
	return 0;
	jieguo[x][y] = jisuan(x + 1,y) + jisuan(x,y + 1);
	return jieguo[x][y];
}
int main()
{
	cin >> n >> m >> a >> b;
	xx[0] = a;xx[1] = a + 1;xx[2] = a + 2;xx[3] = a + 1;xx[4] = a + 2;xx[5] = a - 1;xx[6] = a - 2;xx[7] = a - 1;xx[8] = a - 2;
	yy[0] = b;yy[1] = b + 2;yy[2] = b + 1;yy[3] = b - 2;yy[4] = b - 1;yy[5] = b + 2;yy[6] = b + 1;yy[7] = b - 2;yy[8] = b - 1;
	cout << jisuan(0,0);
	
	return 0;
}

wa3 4,哪位大神看看