#include<bits/stdc++.h>
using namespace std;
const int dx[4]={1,0},dy[4]={0,1};
int n,m,a[21][21],x,y,ans;
void dfs(int x,int y)
{		
	if(x<0||y<0||x>n||y>m||a[x][y]==1) return ;
	if(x==n&&y==m) 
	{
		ans++;
		return ;
	}
	for(int i=0;i<2;i++)
		dfs(x+dx[i],y+dy[i]);
}
int main(){
scanf("%d %d %d %d",&n,&m,&x,&y);
a[x-2][y-1]=1;
a[x-2][y+1]=1;
a[x-1][y-2]=1;
a[x-1][y+2]=1; 
a[x+2][y-1]=1;
a[x+2][y+1]=1;
a[x+1][y-2]=1;
a[x+1][y+2]=1; 
a[x][y]=1;
dfs(0,0);
printf("%d",ans);
    return 0;
}