#include<bits/stdc++.h>
using namespace std;
int zx,zy,mx,my;
long long a[210][210];
long long f(int x,int y){
	//cout<<x<<" "<<y<<" "<<a[x][y]<<endl;
	if(a[x][y]==0)return 0;
	if(x==0||y==0){
		a[x][y]=1;
		return 1;
	}
	else{
		if(a[x][y]==-1){
			a[x][y]=f(x-1,y)+f(x,y-1);
			return a[x][y];
		}
		else return a[x][y];
	}
}
int main(){
	cin>>zx>>zy>>mx>>my;
	for (int i=0;i<=21;i++){
		for(int j=0;j<=21;j++){
			if(i==0||j==0)a[i][j]=1;
			else a[i][j]=-1;
		}
	}
	a[mx+1][my+2]=0;
	a[mx+2][my+1]=0;
	a[mx+1][my-2]=0;
	a[mx+2][my-1]=0;
	a[mx-1][my+2]=0;
	a[mx-2][my+1]=0;
	a[mx-1][my-2]=0;
	a[mx-2][my-1]=0;
	cout<<f(zx,zy)<<endl;
	return 0;
}