#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vint;
typedef pair<int,int> pint;
typedef vector<pint> vpint;
#define rep(i,n) for(int i=0;i<(n);i++)
#define REP(i,n) for(int i=n-1;i>=(0);i--)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
#define all(v) (v).begin(),(v).end()
#define eall(v) unique(all(v), v.end())
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define chmax(a, b) a = (((a)<(b)) ? (b) : (a))
#define chmin(a, b) a = (((a)>(b)) ? (b) : (a))
const int MOD = 1e9 + 7;
const int INF = 1e9;
const ll INFF = 1e18;

int n;
ll d[100010];
ll x, y;
int main() {
	cin >> n;
	rep(i, n) cin >> d[i];
	cin >> x >> y;
	ll dist = abs(x) + abs(y);

	// 1回
	{
		bool f = false;
		rep(i, n) if(dist == d[i]) f = true;
		if(f) {
			printf("1\n"); return 0;
		}
	}

	// 2回
	{
		set<ll> st;
		rep(i, n) st.insert(d[i]);
		bool f = false;
		rep(i, n) {
			ll k = abs(d[i] - dist);
			if(st.count(k)) {
				f = true; break;
			}
		}
		if(f) {
			printf("2\n"); return 0;
		}
	}

	printf("-1\n");
	return 0;
}