#include<bits/stdc++.h>
using namespace std;
int a[25][25];
int t1[9]={0,1,2,2,1,-1,-2,-2,-1};
int t2[9]={0,-2,-1,1,2,2,1,-1,-2};
int main(){
	int x1,y1,x2,y2;
	cin>>x1>>y1>>x2>>y2;
	for(int i=0;i<9;i++){
		if(x2+t1[i]>=0&&y2+t2[i]>=0){
			a[x2+t1[i]][y2+t2[i]]=1;
		}
	}
	/*for(int i=0;i<=x1;i++){
		cout<<endl;
		for(int z=0;z<=y1;z++){
			cout<<a[i][z];
		}
	}*/a[x1+1][y1]=1;//cout<<a[x1+1][y1]<<endl;
	for(int i=y1;i>=0;i--){
		for(int z=x1;z>=0;z--){
			if(a[i][z]==1){
				a[i][z]=0;continue;
			}
			a[i][z]=a[i+1][z]+a[i][z+1];
		}
	}/*
	for(int i=0;i<=x1;i++){
		for(int z=0;z<=y1;z++){
			cout<<a[i][z];
		}
		cout<<endl;
	}*/
	cout<<a[0][0];
	return 0;
}