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.util.*;
public class Main {
    public static void main(String[] args){
      // 入力
      Scanner sc = new Scanner(System.in);
      int X = sc.nextInt();
      int N = sc.nextInt();
      int[] p = new int[N];
      int result = 0;
      if(N == 0){
        result = X;
      }else{
        for(int i = 0; i < N; i++){
          p[i] = sc.nextInt();
        }
      }
      
      // 判定
      if(N != 0){
        boolean[] list = new boolean[102];
        Arrays.fill(list, true);
        for(int i = 0; i < N; i++){
          int index = p[i];
          list[index] = false;
        }
        
        int pos = X;
        int dif = 0;
        boolean judge = list[X];
        while(!judge){
          dif++;
          pos = X - dif;
          judge = list[pos];
          if(!judge){
            pos = X + dif;
            judge = list[pos];
          }
        }
        result = pos;
      }
      
      // 出力
      System.out.println(result);
    }
    

}