#include <iostream>
#include <fstream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <cstring>
#include <string>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <deque>
#include <algorithm>
using namespace std;

#define REP(i,n) for(int i=0; i<n; ++i)
#define FOR(i,a,b) for(int i=a; i<=b; ++i)
#define FORR(i,a,b) for (int i=a; i>=b; --i)
#define ALL(c) (c).begin(), (c).end()

typedef long long ll;
typedef vector<int> VI;
typedef vector<ll> VL;
typedef vector<VI> VVI;
typedef vector<VL> VVL;
typedef pair<int,int> P;
typedef pair<ll,ll> PL;

int main() {
    int n;
    cin >> n;
    VL d(n);
    set<ll> st;
    REP(i,n){
        scanf("%lld", &d[i]);
        st.insert(d[i]);
    }
    sort(ALL(d));

    ll xx, yy;
    cin >> xx >> yy;
    ll x = xx + yy, y = xx - yy;
    x = abs(x);
    y = abs(y);
    if (y > x) swap(x, y);

    REP(i,n){
        if (d[i] == x){
            cout << 1 << endl;
            return 0;
        }
    }

    REP(i,n){
        if (st.count(abs(x - d[i]))){
            cout << 2 << endl;
            return 0;
        }
    }

    VL d_even, d_odd;
    REP(i,n){
        if (d[i] % 2 == 0) d_even.push_back(d[i]);
        else d_odd.push_back(d[i]);
    }
    d_even.push_back(1e17);
    d_odd.push_back(1e17);

    for (int d : d_even){
        if (y % 2 == 0){
            ll p = *lower_bound(ALL(d_even), abs(x - d));
            if (p <= x + d){
                cout << 2 << endl;
                return 0;
            }
        }else{
            ll p = *lower_bound(ALL(d_odd), abs(x - d));
            if (p <= x + d){
                cout << 2 << endl;
                return 0;
            }
        }
    }
    for (int d : d_odd){
        if (y % 2 == 0){
            ll p = *lower_bound(ALL(d_odd), abs(x - d));
            if (p <= x + d){
                cout << 2 << endl;
                return 0;
            }
        }else{
            ll p = *lower_bound(ALL(d_even), abs(x - d));
            if (p <= x + d){
                cout << 2 << endl;
                return 0;
            }
        }
    }
    cout << -1 << endl;

    return 0;
}