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

int main(){
    int n;
    cin >> n;
    int move_mass[n];
    int parity_max[2] = {0, 0};
    for(int i = 0; i < n; i++){
        cin >> move_mass[i];
        parity_max[move_mass[i] % 2] = max(parity_max[move_mass[i] % 2], move_mass[i]);
    }
    int x, y;
    cin >> x >> y;
    sort(move_mass, move_mass + n);
    for(int i = 0; i < n; i++){
        if(move_mass[i] == abs(x) + abs(y)){
            cout << 1 << endl;
            return 0;
        }
    }
    if(((abs(x) + abs(y)) % 2 == 0 && max(parity_max[0], parity_max[1]) * 2 >= abs(x) + abs(y)) || parity_max[0] + parity_max[1] >= (abs(x) + abs(y))){
        cout << 2 << endl;
        return 0;
    }
    cout << -1 << endl;
}