#include<iostream>
#include<cstring>
#include<string>
#include<cstdio>
#include<queue>
#include<cmath>
#include<algorithm>
using namespace std;
int xx[9] = {0, -2, -1, 1, 2, 2, 1, -1, -2};
int xy[9] = {0, 1, 2, 2, 1, -1, -2, -2, -1};
int a[22][22],book[22][22];
int ax[2]={1,0};
int ay[2]={0,1};
int ans=0;
int mx,my,bx,by;
void dfs(int fx,int fy){
	if(fx==bx&&fy==by){
		ans++;
		return;
	}
	for(int i=0;i<=1;i++){
		int dx=fx+ax[i];
		int dy=fy+ay[i];
		if(dx<0||dy<0||dx>bx||dy>by)continue;
		if(book[dx][dy]==0){
			book[dx][dy]=1;
			dfs(dx,dy);
			book[dx][dy]=0;
		}
	}
}
int main(){
	cin >>bx>>by>>mx>>my;
	for(int j=0;j<9;j++){
		book[mx+xx[j]][my+xy[j]]=2;
	} 
	book[0][0]=1;
	dfs(0,0);
	cout <<ans;
	return 0;
}