#include <iostream>
using namespace std;
bool ed[21][21];
int movex[2] = { 1,0 }, movey[2] = { 0,1 };
int movehx[8] = { 1, 2, -1, -2,1,2,-1,-2 }, movehy[8] = { 2, 1, -2, -1,-2,-1,2,1 };
struct path
{
	int x = 0, y = 0;
};
void horse(int bx, int by, int hx, int hy,bool ed[21][21])
{
	ed[hx][hy] = true;
	for (int i = 0; i < 8; i++)
	{
		if (hx + movehx[i] <= bx && hy + movehy[i] <= by&& hx + movehx[i]>=0&& hy + movehy[i]>=0)
		{
			int x = hx + movehx[i], y = hy + movehy[i];
			ed[x][y] = true;
		}
	}
}
void way(path a,bool ed[21][21],int &n,int bx,int by)
{
	if (a.x == bx && a.y == by) { n++; return; }
	for (int i = 0; i < 2; i++)
		{
			a.x += movex[i], a.y += movey[i];
			
			if (!ed[a.x][a.y]&&a.x <= bx && a.y <= by) 
			 way(a, ed, n, bx, by); 
			a.x -= movex[i], a.y -= movey[i];
		}
	return;
}

int main()
{
	path a;
	int sum = 0;
	int bx,  by,  hx,  hy;
	cin >> bx >> by >> hx >> hy;
	horse(bx, by, hx, hy, ed);
	way(a, ed, sum, bx, by); cout << sum;
}