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

typedef long long   signed int LL;
typedef long long unsigned int LU;

#define incID(i, l, r) for(int i = (l)    ; i <  (r); i++)
#define incII(i, l, r) for(int i = (l)    ; i <= (r); i++)
#define decID(i, l, r) for(int i = (r) - 1; i >= (l); i--)
#define decII(i, l, r) for(int i = (r)    ; i >= (l); i--)
#define  inc(i, n) incID(i, 0, n)
#define inc1(i, n) incII(i, 1, n)
#define  dec(i, n) decID(i, 0, n)
#define dec1(i, n) decII(i, 1, n)

#define inII(v, l, r) ((l) <= (v) && (v) <= (r))
#define inID(v, l, r) ((l) <= (v) && (v) <  (r))

#define PB push_back
#define EB emplace_back
#define MP make_pair
#define FI first
#define SE second
#define PQ priority_queue

#define  ALL(v)  v.begin(),  v.end()
#define RALL(v) v.rbegin(), v.rend()
#define  FOR(it, v) for(auto it =  v.begin(); it !=  v.end(); ++it)
#define RFOR(it, v) for(auto it = v.rbegin(); it != v.rend(); ++it)

template<typename T> bool   setmin(T & a, T b) { if(b <  a) { a = b; return true; } else { return false; } }
template<typename T> bool   setmax(T & a, T b) { if(b >  a) { a = b; return true; } else { return false; } }
template<typename T> bool setmineq(T & a, T b) { if(b <= a) { a = b; return true; } else { return false; } }
template<typename T> bool setmaxeq(T & a, T b) { if(b >= a) { a = b; return true; } else { return false; } }
template<typename T> T gcd(T a, T b) { return (b == 0 ? a : gcd(b, a % b)); }
template<typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }

// ---- ----

template<typename T> T mod(T x, T y) { return (x % y + y) % y; }

LL n, d[100002], x, y, z;
vector<LL> v[2];

LL solve() {
	if(z == 0) { return 0; }
	inc(i, n) { if(z == d[i]) { return 1; } }
	
	inc(i, n) { v[mod(d[i], 2LL)].PB(d[i]); }
	inc(i, 2) { sort(RALL(v[i])); }
	
	if(z % 2 == 0) {
		if(v[0].size() != 0 && z <= v[0][0] * 2) { return 2; }
		if(v[1].size() != 0 && z <= v[1][0] * 2) { return 2; }
	} else {
		inc(i, v[0].size()) {
			if(v[1].size() == 0) { break; }
			LL ma = max(v[1][0], v[0][i]);
			LL mi = min(v[1][0], v[0][i]);
			if(inII(z, ma - mi, ma + mi)) { return 2; }
		}
		inc(i, v[1].size()) {
			if(v[0].size() == 0) { break; }
			LL ma = max(v[0][0], v[1][i]);
			LL mi = min(v[0][0], v[1][i]);
			if(inII(z, ma - mi, ma + mi)) { return 2; }
		}
	}
	
	return -1;
}

int main() {
	cin >> n;
	inc(i, n) { cin >> d[i]; }
	cin >> x >> y;
	
	z = abs(x) + abs(y);
	
	cout << solve() << endl;
	
	return 0;
}