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: Wrong Answer)

import java.util.Scanner;
public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int x = sc.nextInt();
        int n = sc.nextInt();
        int[] p = new int[n];
        for(int i = 0 ; i < n ; i++ ){
            p[i] = sc.nextInt();
        }
        int[] q = new int[n];
        for(int i = 0 ; i < n ; i++ ){
            q[i] = p[i] - x;
        }
        int che = -1;
        for(int i = 0 ; i < n && che == -1;i++){
            int s = 0;
            int f = 0;
            for(int t = 0 ; t < n; t++){
                if(q[t] == i){
                    s++;
                }
                if(q[t] == -i){
                    f++;
                }
            }
            if(s == 0 || f == 0){
                che = i;
            }
        }
        int se = 0;
        for(int o = 0; o < n ; o++){
            if(q[o] == -che){
                se = 1;
            }
        }
        if(n == 0){
            System.out.println(x);
        }else if(se == 1){
            System.out.println(x + che);
        }else{
            System.out.println(x - che);
        }
        sc.close();
    }
}