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

int main(){
    int n;
    cin >> n;
    int move_mass[n];
    for(int i = 0; i < n; i++){
        cin >> move_mass[i];
    }
    int x, y;
    cin >> x >> y;
    for(int i = 0; i < n; i++){
        if(move_mass[i] == abs(x) + abs(y)){
            cout << 1 << endl;
            return 0;
        }
    }
    for(int i = 0; i < n; i++){
        if(upper_bound(move_mass, move_mass + n, abs(x) + abs(y) + move_mass[i]) -
           lower_bound(move_mass, move_mass + n, abs(x) + abs(y) + move_mass[i]) ||
           upper_bound(move_mass, move_mass + n, abs(x) + abs(y) - move_mass[i]) -
           lower_bound(move_mass, move_mass + n, abs(x) + abs(y) - move_mass[i])){
            cout << 2 << endl;
            return 0;
        }
    }
    cout << -1 << endl;
}