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.InputStream;
import java.io.PrintStream;
import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

public class Main {

  public static void main(String[] args) {
    resolve(System.in, System.out);
  }

  static void resolve(InputStream is, PrintStream pw) {
    Scanner sc = new Scanner(is);
    int x = Integer.parseInt(sc.next());
    int n = Integer.parseInt(sc.next());
    Set<Integer> forbidden = new HashSet<>();
    for (int i = 0; i < n; i++) {
      int p = Integer.parseInt(sc.next());
      forbidden.add(p);
    }
    int min = Integer.MAX_VALUE;
    int ans = -10;
    for (int i = -10; i <= 110; i++) {
      if (forbidden.contains(i)) {
        continue;
      }
      int abs = Math.abs(x - i);
      if (abs < min) {
        ans = i;
        min = abs;
      }
    }
    pw.println(ans);
  }
}