using namespace std;

int main()
{
    int cx[]={0, -2, -1, 1, 2, 2, 1, -1, -2};
    int cy[]={0, 1, 2, 2, 1, -1, -2, -2, -1};

	int w[21][21]={};
	bool s[21][21];
	int x,y,a,b;
    cin>>x>>y>>a>>b;
    x += 2;y += 2;a += 2;b += 2;
	
	w[2][1]=1;
	s[x][y]=1;
	for(int i=1;i<=8;i++)
	s[x+cx[i]][y+cy[i]]=1;
	
	for(int i=2;i<=a;i++)
	{
		for(int j=2;j<=b;j++){
			if(s[i][j]) continue;
		w[i][j]=w[i-1][j]+w[i][j-1];
		}
	}
	cout<<w[a][b];
	return 0;
	
}