#include <bits/stdc++.h>

using namespace std;

const int MAX = 1e5 + 10;
int n;
long long d[MAX];
long long x, y;

int main() {
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    scanf("%lld", d + i);
  }
  scanf("%lld%lld", &x, &y);
  sort(d, d + n);
  if (x == 0 && y == 0) {
    cout << 0 << endl;
    return 0;
  }
  x = llabs(x);
  y = llabs(y);
  for (int i = 0; i < n; i++) {
    if (d[i] == x + y) {
      cout << 1 << endl;
      return 0;
    }
  }
  for (int i = 0; i < n; i++) {
    int low = i + 1, high = n;
    while (high - low > 5) {
      int mid = (high + low) / 2;
      if (d[i] + d[mid] <= x + y) {
        low = mid;
      } else {
        high = mid;
      }
    }
    for (int j = low; j <= high; j++) {
      if (d[i] + d[j] == x + y) {
        cout << 2 << endl;
        return 0;
      }
    }
  }
  // 遠くに行って戻ってくる
  reverse(d, d + n);
  for (int i = 0; i < n; i++) {
    int low = i + 1, high = n;
    while (high - low > 5) {
      int mid = (high + low) / 2;
      if (d[i] - d[mid] <= x + y) {
        high = mid;
      } else {
        low = mid;
      }
    }
    for (int j = low; j <= high; j++) {
      if (d[i] - d[j] == x + y) {
        cout << 2 << endl;
        return 0;
      }
    }
  }
  cout << -1 << endl;
}