#include <bits/stdc++.h>

using namespace std;

#define int long long
//using LL = long long int;
using II = pair<int, int>;

const int MAX_N = 100005;

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

signed main()
{
  cin >> N;
  for(int i = 0; i < N; i++) {
    cin >> D[i];
  }
  cin >> X >> Y;

  int XYD = abs(X) + abs(Y);

  if(X == 0 && Y == 0) {
    cout << 0 << endl;
    return 0;
  }

  set<int> S;
  for(int i = 0; i < N; i++) {
    if(XYD == D[i]) {
      cout << 1 << endl;
      return 0;
    }
    S.insert(D[i]);
    S.insert(-D[i]);
  }

  for(int i = 0; i < N; i++) {
    if(S.find(XYD - D[i]) != S.end() || S.find(D[i] - XYD) != S.end()) {
      cout << 2 << endl;
      return 0;
    }
  }

  cout << -1 << endl;

  return 0;
}