import java.io.*;
import java.util.*;
import java.util.stream.*;

import static java.lang.Math.*;

class FastScanner { // {{{
  private final InputStream in = System.in;
  private final byte[] buffer = new byte[1024];
  private int ptr = 0;
  private int buflen = 0;
  private boolean hasNextByte() {
    if(ptr < buflen) { return true; }
    ptr = 0;
    try {
      buflen = in.read(buffer);
    } catch(IOException ex) {
      ex.printStackTrace();
    }
    if(buflen <= 0) { return false; }
    return true;
  }
  private int readByte() { if(hasNextByte()) { return buffer[ptr++]; } return -1; }
  private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126; }
  private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) { ++ptr; } }
  public boolean hasNext() { skipUnprintable(); return hasNextByte(); }
  public String next() {
    if(!hasNext()) { throw new NoSuchElementException(); }
    StringBuilder sb = new StringBuilder();
    int b = readByte();
    while(isPrintableChar(b)) {
      sb.appendCodePoint(b);
      b = readByte();
    }
    return sb.toString();
  }
  public long nextLong() {
    if(!hasNext()) { throw new NoSuchElementException(); }
    long n = 0;
    boolean minus = false;
    int b = readByte();
    if(b == '-') {
      minus = true;
      b = readByte();
    }
    if(b < '0' || '9' < b) { throw new NumberFormatException(); }
    while(true) {
      if('0' <= b && b <= '9') {
        n *= 10;
        n += b - '0';
      } else if(b == -1 || !isPrintableChar(b)) {
        return minus ? -n : n;
      } else {
        throw new NumberFormatException();
      }
      b = readByte();
    }
  }
  public int nextInt() {
    if(!hasNext()) { throw new NoSuchElementException(); }
    int n = 0;
    boolean minus = false;
    int b = readByte();
    if(b == '-') {
      minus = true;
      b = readByte();
    }
    if(b < '0' || '9' < b) { throw new NumberFormatException(); }
    while(true) {
      if('0' <= b && b <= '9') {
        n *= 10;
        n += b - '0';
      } else if(b == -1 || !isPrintableChar(b)) {
        return minus ? -n : n;
      } else {
        throw new NumberFormatException();
      }
      b = readByte();
    }
  }
} // }}}

public class Main {
  private long[] d;
  private int n;
  private long x, y;

  // [lo, hi)
  boolean exist(long x, int lo, int hi) {
    int pos = Arrays.binarySearch(d, lo, hi, x);
    return pos >= 0 && d[pos] == x;
  }

  int f(long x, long y) {
    if(x == 0 && y == 0) { return 2; }
    long dist = abs(x) + abs(y);
    if(exist(dist, 0, n)) { return 1; }
    for(int i=0; i<n; ++i) {
      long left0  = dist - d[i];
      long aleft0 = abs(left0);
      long left1  = dist + d[i];
      if(exist(aleft0, 0, n)) { return 2; }
      if(exist(left1, 0, n)) { return 2; }
    }
    return -1;
  }

  private void solve() {
    FastScanner sc = new FastScanner();
    n = sc.nextInt();
    d = new long[n];
    for(int i=0; i<n; ++i) {
      d[i] = sc.nextLong();
    }
    Arrays.sort(d);
    long x = sc.nextLong(),
         y = sc.nextLong();
    int res = f(x, y);
    System.out.println(res);
  }

  public static void main(String[] args) {
    new Main().solve();
  }
}