/* -*- coding: utf-8 -*-
 *
 * 602.cc: No.602 隠されていたゲーム2 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100000;

/* typedef */

typedef long long ll;

/* global variables */

ll eds[MAX_N], ods[MAX_N];

/* subroutines */

bool findg(int n, ll ds[], ll v) {
  int k = lower_bound(ds, ds + n, v) - ds;
  return (k < n && ds[k] == v);
}

/* main */

int main() {
  int n;
  scanf("%d", &n);

  int en = 0, on = 0;
  for (int i = 0; i < n; i++) {
    ll di;
    scanf("%lld", &di);
    if (di & 1) ods[on++] = di;
    else eds[en++] = di;
  }
  //printf("en=%d, on=%d\n", en, on);

  ll gx, gy;
  scanf("%lld%lld", &gx, &gy);
  ll gd = abs(gx) + abs(gy);
  //printf("gd=%d\n", gd);

  if (gd == 0) {
    puts("0");
    return 0;
  }

  sort(eds, eds + en);
  sort(ods, ods + on);

  if (((gd & 1) && findg(on, ods, gd)) ||
      (! (gd & 1) && findg(en, eds, gd))) {
    puts("1");
    return 0;
  }

  if (gd & 1) {
    for (int i = 0; i < en; i++) {
      ll &edi = eds[i];
      int j = lower_bound(ods, ods + on, abs(gd - edi)) - ods;
      int k = upper_bound(ods, ods + on, gd + edi) - ods;
      if (j < k) {
	puts("2");
	return 0;
      }
    }
  }
  else {
    for (int i = 0; i < en; i++) {
      ll &edi = eds[i];
      int j = lower_bound(eds, eds + en, abs(gd - edi)) - eds;
      int k = upper_bound(eds, eds + en, gd + edi) - eds;
      if (j < k) {
	puts("2");
	return 0;
      }
    }
    for (int i = 0; i < on; i++) {
      ll &odi = ods[i];
      int j = lower_bound(ods, ods + on, abs(gd - odi)) - ods;
      int k = upper_bound(ods, ods + on, gd + odi) - ods;
      if (j < k) {
	puts("2");
	return 0;
      }
    }
  }
  
  puts("-1");
  return 0;
}