#include<iostream>
using namespace std;
int a[101][101];
int vis[101][101];
int main(){
	int x1,y1,x2,y2;
	cin>>x1>>y1>>x2>>y2;
	x1++,y1++,x2++,y2++;
	vis[x1][y1]=1;
    vis[x1-2][y1+1]=1;
    vis[x1-1][y1+2]=1;
    vis[x1+1][y1+2]=1;
    vis[x1+2][y1+1]=1;
    vis[x1+2][y1-1]=1;
    vis[x1+1][y1-2]=1;
    vis[x1-1][y1-2]=1;
    vis[x1-2][y1-1]=1;
	for(int i=1;i<=x2;i++){
        for(int j=1;j<=y2;j++){
            if(i==1&&j==1){
                a[i][j]=1;
                a[1][j]=1;
            }else if(i==1) {
                a[i][j]=vis[i][j]==0?a[i][j-1] : 0;
            }else if(j==1){
                a[i][j]=vis[i][j]==0?a[i-1][j] : 0;
            }else{
                a[i][j]=vis[i][j]==0?a[i-1][j]+a[i][j-1] : 0;
            }
        }
    }
	cout<<a[x2][y2]<<endl;
	return 0;
}