#include<bits/stdc++.h>
using namespace std;
bool a[30][30];
int n,m;
int n1,m1;
long long sum=0;
void dfs(int x,int y){
	if(x==n&&y==m)sum++;
	//cout<<x<<" "<<y<<"\n";
	if(!a[x+1][y]&&x+1<=n)dfs(x+1,y);
	if(!a[x][y+1]&&y+1<=m)dfs(x,y+1);
	return ;
}
int main() {
    cin>>n>>m>>n1>>m1;
     for(int i=0;i<=n;i++){
    	for(int j=0;j<=m;j++)a[i][j]=0;
	}
    a[n1][m1]=a[n1-1][m1-2]=a[n1-2][m1-1]=a[n1+2][m1-1]=a[n1+1][m1-2]=a[n1+1][m1+2]=a[n1+2][m1+1]=a[n1-2][m1+1]=a[n1-1][m1+2]=1;
  /*  for(int i=0;i<=n;i++){
    	for(int j=0;j<=m;j++)cout<<a[i][j];
    	cout<<"\n";
	}*/
	dfs(0,0);
	cout<<sum;
    return 0;
}