#include <iostream>
#include <iomanip>
#include <cstring>
#include <algorithm> 
#include <math.h>
#include <queue>
#include <functional>
#include <map>
#include <vector>
#include <string>
using namespace std;
typedef long long ll;

int n;
ll x, y, d[100005];
int main(void){
    cin >> n;
    ll a[4];
    for (int i = 0; i < 4; i++) a[i] = -1000000005;

    for (int i = 0; i < n; i++) cin >> d[i];

    sort(d, d + n);
    for (int i = n - 1; i >= 0; i--){
        if (d[i] % 2 == 0){
            for (int j = 0; j < 2; j++){
                if (a[j] < 0){
                    a[j] = d[i];
                    break;
                }
            }
        }
        else{
            for (int j = 2; j < 4; j++){
                if (a[j] < 0){
                    a[j] = d[i];
                    break;
                }
            }
        }
    }
    cin >> x >> y;

    ll D = max(x, -x) + max(y, -y);

    for (int i = 0; i < n; i++){
        if (D == d[i]){
            cout << 1 << endl;
            return 0;
        }
    }

    for (int i = 0; i < 4; i++){
        for (int j = i + 1; j < 4; j++){
            if ((D + a[i] + a[j]) % 2 == 0 && a[i] + a[j] >= D){
                if (a[i] == 1 || a[j] == 1){
                    if (a[i] + a[j] != D + 1)continue;
                }
                cout << 2 << endl;
                return 0;
            }
        }
    }

    cout << -1 << endl;

}