Problem:
Score : 300 points

Problem Statement

Given are an integer X and an integer sequence of length N: p_1, \ldots, p_N.

Among the integers not contained in the sequence p_1, \ldots, p_N (not necessarily positive), find the integer nearest to X, that is, find the integer whose absolute difference with X is the minimum. If there are multiple such integers, report the smallest such integer.

Constraints

1 \leq X \leq 100

0 \leq N \leq 100

1 \leq p_i \leq 100

p_1, \ldots, p_N are all distinct.

All values in input are integers.

Input

Input is given from Standard Input in the following format:

X N
p_1 ... p_N

Output

Print the answer.

Sample Input 1

6 5
4 7 10 6 5

Sample Output 1

8

Among the integers not contained in the sequence 4, 7, 10, 6, 5, the one nearest to 6 is 8.

Sample Input 2

10 5
4 7 10 6 5

Sample Output 2

9

Among the integers not contained in the sequence 4, 7, 10, 6, 5, the ones nearest to 10 are 9 and 11. We should print the smaller one, 9.

Sample Input 3

100 0

Sample Output 3

100

When N = 0, the second line in the input will be empty. Also, as seen here, X itself can be the answer.

Solution in Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.io.PrintWriter;
import java.util.*;
import java.util.Scanner;

// Solution
public class Main {
  private static Scanner in;
  private static PrintWriter out;
  private static final String INPUT = ""; // input file name

  /**
   * Interactive get next command
   */
  static int get(int pos) {
    out.println(pos + 1);
    out.flush();
    return ni();
  }

  static void solve() {
    int x = ni();
    int n = ni();

    int[] arr = new int[n];
    Set<Integer> s = new HashSet<>();
    for (int i = 0; i <n ;i++) {
    	arr[i] = ni();
      s.add(arr[i]);
    }
    
    Arrays.sort(arr);
    
    int t = x;
    int a = x; int b = x;
    
    while (true) {
      if (s.contains(a)) {
      	a--;
      } else {
      	out.println(a);
        break;
      }
      
      if (s.contains(b)) {
      	b++;
      } else {
      	out.println(b);
        break;
      }
    }
  }

  public static void main(String[] args) throws Exception {
    long S = System.currentTimeMillis();
    in = INPUT.isEmpty() ? new Scanner(System.in) : new Scanner(INPUT);
    out = new PrintWriter(System.out);

    solve();
    out.flush();
    long G = System.currentTimeMillis();
    tr(G - S + "ms");
  }

  private static int ni() {
    return Integer.parseInt(in.next());
  }

  private static long nl() {
    return Long.parseLong(in.next());
  }

  // Math Utils
  private static int pi(int num, int pow) {
    int result = 1;

    while (pow > 0) {
      if (pow % 2 == 1) {
        result *= num;
      }

      num *= num;
      pow /= 2;
    }

    return result;
  }

  private static int pim(int num, int pow, int mod) {
    int result = 1;

    while (pow > 0) {
      if (pow % 2 == 1) {
        // keep collecting `odd` num in result
        result = (result * num) % mod;
      }

      num = (num * num) % mod;
      pow /= 2;
    }

    return result;
  }

  private static long pl(long num, long pow) {
    long result = 1;

    while (pow > 0) {
      if (pow % 2 == 1) {
        result *= num;
      }

      num *= num;
      pow /= 2;
    }

    return result;
  }

  private static long plm(long num, long pow, long mod) {
    long result = 1;

    while (pow > 0) {
      if (pow % 2 == 1) {
        // keep collecting `odd` num in result
        result = (result * num) % mod;
      }

      num = (num * num) % mod;
      pow /= 2;
    }

    return result;
  }

  static void tr(Object... o) {
    if (!INPUT.isEmpty())
      out.println(Arrays.deepToString(o));
  }
}