#include<bits/stdc++.h>
using namespace std;
int dx[4]={1,2,-1,-2};
int dy[4]={2,1,-2,-1};
int sx,sy,fx,fy,ans;
bool c[100][100];
void dfs(int x,int y){
	if(x==fx&&y==fy){
		ans++;
		return ;
	}
	for(int i=0;i<4;i++){
		int a=x+dx[i];
		int b=y=dy[i];
		if(a<1||b<1||a>fx||b>fy||c[a][b]==1) continue;
		c[a][b]=1;
		dfs(a,b);
		c[a][b]=0;
	}
}
signed main(){
	cin>>fx>>fy>>sx>>sy;
	c[sx][sy]=1;
	cout<<ans;
	return 0;
}`