#include<bits/stdc++.h>
using namespace std;
int bx,by,mx,my;
const int dx[2]={0,1};
const int dy[2]={1,0};
const int mmx[8]={-1,1,-2,2,-2,2,-1,1};
const int mmy[8]={-2,-2,-1,-1,1,1,2,2};
long long ans;
bool f[21][21];
void work(int x,int y){
	if(x==bx&&y==by){
		ans++;
		return;
	}
	if(x<0||y<0||x>bx||y>by||f[x][y]==1)return;
	for(int i=0;i<2;i++)work(x+dx[i],y+dy[i]); 
}
int main(){
	cin>>bx>>by>>mx>>my;
	f[mx][my]=1;
	for(int i=0;i<8;i++){
		if(mx+mmx[i]>=0&&my+mmy[i]>=0&&mx+mmx[i]<=bx&&my+mmy[i]<=by)
		f[mx+mmx[i]][my+mmy[i]]=1;
	}
	work(0,0);
	cout<<ans;
	return 0;
}```