#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define mt make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define pb push_back
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

int N, D[100005], X, Y;

int solve() {
    if (X == 0 && Y == 0)return 0;

    int d = abs(X) + abs(Y);
    rep(i, N)if (d == D[i]) return 1;

    sort(D, D + N);
    if (d % 2 == 0) {
        return d <= 2 * D[N - 1] ? 2 : -1;
    }

    int o = -1, e = -1;
    rep(i, N) {
        if (D[i] & 1)o = D[i];
        else e = D[i];
        if (o == -1 || e == -1)continue;
        int l = abs(o - e), r = o + e;
        if (l <= d && d <= r)return 2;
    }
    
    return -1;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> N;
    rep(i, N)cin >> D[i];
    cin >> X >> Y;
    
    cout << solve() << endl;
}