import java.util.*;
import java.lang.*;
import java.io.*;

public class Main
{
  public static void main (String[] args) throws java.lang.Exception
  {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int []arr = new int[n];
    for (int i = 0; i < n; i++) {
      arr[i] = sc.nextInt();
    }
    int B = sc.nextInt();
    int count = 0;
    HashMap<Integer, Integer>diff = new HashMap<>();

    for (int i = 0; i < n; i++) {
        diff.put(arr[i], 1);
      if (diff.containsKey(B + arr[i])) {
        count=1;
      }
      if (diff.containsKey(B - arr[i])) {
        count=1;
      }

    }
    System.out.print(count);
  }
}