#include<bits/stdc++.h>
using namespace std;
int dx[8]={-2,-2,-1,1,2,2,1,-1};
int dy[8]={-1,1,2,2,1,-1,-2,-2};
int arr[25][25];
int main(){
	int ax,ay,bx,by,hx,hy;
	cin>>bx>>by>>hx>>hy;
	for(int i=0;i<8;i++){
		arr[hx+dx[i]][hy+dy[i]]=-1;
	}
	arr[0][0]=1;
	for(int i=0;i<=bx;i++){
		for(int j=0;j<=by;j++){
			if(arr[i][j]==-1||(i==0&&j==0)){
				continue;
			}
			if(i==0){
				arr[i][j]=max(arr[i][j-1],0);
				continue;
			}
			if(j==0){
				arr[i][j]=max(arr[i-1][j],0);
				continue;
			}
			arr[i][j]=max(arr[i-1][j],0)+max(arr[i][j-1],0);
		}
	}
	cout<<arr[bx][by]<<"\n";
	return 0;
}