#include<iostream>
using namespace std;
int a[25][25] = {0};
int i = 0,j = 0;
int dp(int i,int j,int n,int m){
	if(i == n&&j == m)return 1;
	if(a[i][j] == 1)return 0;
	if(i > n || j > m)return 0;	
	if(i <= n && j <= m && a[i][j] != 1){
	return dp(i+1,j,n,m) + dp(i,j+1,n,m);
}
}
int main(){
	int n,m,n1,m1;
	cin >> n >> m >> n1 >> m1;
	a[n1][m1] = 1;
	a[n1+2][m1-1] = 1;
	a[n1+1][m1-2] = 1;
	a[n1-1][m1-2] = 1;
	a[n1-2][m1-1] = 1;
	a[n1-2][m1+1] = 1;
	a[n1-1][m1+2] = 1;
	a[n1+1][m1+2] = 1;
	a[n1+2][m1+1] = 1;
	cout << dp(i,j,n,m);
	return 0;
}