#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

int main(){
    int n;
    cin >> n;
    int move_mass[n];
    vector<int> even_odd[2];
    int number_max = 0;
    for(int i = 0; i < n; i++){
        cin >> move_mass[i];
        number_max = max(number_max, move_mass[i]);
        even_odd[move_mass[i] % 2].push_back(move_mass[i]);
    }
    int x, y;
    cin >> x >> y;
    int distance = abs(x) + abs(y);
    if(!distance){
        cout << 0 << endl;
    }
    sort(move_mass, move_mass + n);
    sort(even_odd[0].begin(), even_odd[0].end());
    sort(even_odd[1].begin(), even_odd[1].end());
    for(int i = 0; i < n; i++){
        if(move_mass[i] == distance){
            cout << 1 << endl;
            return 0;
        }
    }
    int min_difference = 0;
    int look_not_odd = 0;
    int look_odd = 0;
    while(look_not_odd != even_odd[0].size() && look_odd != even_odd[1].size()){
        min_difference = min(min_difference, abs(even_odd[0][look_not_odd] - even_odd[1][look_odd]));
        if(even_odd[0][look_not_odd] > even_odd[1][look_odd]){
            look_odd++;
        }else{
            look_not_odd++;
        }
    }
    if(distance % 2 == 0){
        if(number_max * 2 >= distance){
            cout << 2 << endl;
        }else{
            cout << -1 << endl;
        }
    }else if(even_odd[0].size() && even_odd[1].size()){
        if(min_difference <= distance && distance <= even_odd[0].back() + even_odd[1].back()){
            cout << 2 << endl;
        }else{
            cout << -1 << endl;
        }
    }else{
        cout << -1 << endl;
    }
}