#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; }

// ---- ----

LL n, d[100000], x, y, z;

bool ok(LL a, LL b) {
	LL ma = max(a, b);
	LL mi = min(a, b);
	return inII(z, ma - mi, ma + mi);
}

LL solve() {
	if(z == 0) { return 0; }
	inc(i, n) { if(z == d[i]) { return 1; } }
	
	if(z % 2 == 0) {
		LL ma = 0;
		inc(i, n) { setmax(ma, d[i]); }
		if(z <= ma * 2) { return 2; }
	} else {
		vector<LL> v[2];
		inc(i, n) { v[d[i] % 2].PB(d[i]); }
		inc(i, 2) { sort(ALL(v[i])); }
		LL s0 = v[0].size();
		LL s1 = v[1].size();
		if(s0 == 0 || s1 == 0) { return -1; }
		
		int p = -1;
		inc(j, s1) { if(v[1][j] <= z) { p = j; } }
		int j = 0;
		inc(i, s0) {
			if(v[0][i] <= z) {
				if(inID(p + 0, 0, s1) && ok(v[0][i], v[1][p + 0])) { return 2; }
				if(inID(p + 1, 0, s1) && ok(v[0][i], v[1][p + 1])) { return 2; }
			} else {
				while(j < s1 && v[0][i] > v[1][j] + z) { j++; }
				if(j >= s1) { break; }
				if(ok(v[0][i], v[1][j])) { 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;
}