#include <bits/stdc++.h>

using namespace std;

int main()
{
  int N, D[100000], X, Y;

  cin >> N;

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

  cin >> X >> Y;


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

  int F = abs(X) + abs(Y);
  for(int i = 0; i < N; i++) {
    if(F == D[i]) {
      cout << 1 << endl;
      return (0);
    }
  }

  sort(D, D + N);
  for(int i = 0; i < N; i++) {
    int sa = F - D[i];
    auto p = lower_bound(D, D + N, sa) - D;
    if(p == N) continue;
    if(D[p] == sa) {
      cout << 2 << endl;
      return (0);
    }
  }


  cout << -1 << endl;
}