#include <bits/stdc++.h>
using namespace std;

int n, x, y, a, t, r=-1;
int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	cin >> n;
	int d[n];
	for (int i = 0; i < n; ++i) cin >> d[i];
	cin >> x >> y;
	a = abs(x) + abs(y);
	for (int i = 0; i < n; ++i) {
		t = d[i];
		if (d[i]==a) r = 1;
		else if (binary_search(d+i+1, d+n, abs(a-t)) || binary_search(d+i+1, d+n, a+t)) 
			r = 2;
		if (r!=-1) break;
	}
	cout << r << "\n";
}