#include<iostream>
#include<string>
#include<algorithm>
#define ll long long
using namespace std;
 
const int fx[] = { 0,-2,-1,1,2,2,1,-1,-2 };
const int fy[] = { 0,1,2,2,1,-1,-2,-2,-1 };
//马可以走到的位置
 
int bx, by, nx, my;
ll lj[40][40];
bool s[40][40];//判断这个点能不能走
 
int main()
{
	//c scanf输入数据 printf输出数据
	cin >> bx >> by >> nx >> my;
	bx += 2; by += 2; nx += 2; my += 2;
	lj[1][2] = 1;//初始化让lj[2][2]=1；
	s[nx][my] = 1;
	for (int i = 1; i <= 8; i++)
	{
		s[nx + fx[i]][my + fy[i]] = 1;
	}
	for(int i=2;i<=bx;i++)
		for (int j = 2; j <=by; j++)
		{
			if (s[i][j])
			{
				continue;//lj[i][j] = 0;
			}
			lj[i][j] = lj[i - 1][j] + lj[i][j - 1];
		}
	cout << lj[bx][by] << endl;
	//return 0;
}
// 
//     	   __  __          __  
//  	  / / / /_  ______/ /________ 
//       / /_/ / / / / __  / ___/ __ \
//  	/ __  / /_/ / /_/ / /  / /_/ /
//     /_/ /_/\__, /\__,_/_/   \____/ 
//           /____/                   
//