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.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.StringTokenizer;

public class Main {
    public static void main(String []args) throws IOException {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer(br.readLine());
        int x=Integer.parseInt(st.nextToken());
        int n=Integer.parseInt(st.nextToken());
        HashSet<Integer> num = new HashSet<>();
        int c=1;
        int temp1=x;
        int temp2=x;
        boolean f1=false;
        boolean f2=false;
        if(n==0){
            System.out.println(x);
        }
        else {
            st = new StringTokenizer(br.readLine());
            for (int i = 0; i < n; i++) {
                num.add(Integer.parseInt(st.nextToken()));
            }
            while (c<num.size()) {
                temp1 = x + c;
                temp2 = x - c;
                if (!num.contains(temp2)) {
                    f2 = true;
                    break;
                }
                if (!num.contains(temp1)) {
                    f1 = true;
                    break;
                }
                c++;
            }
            if(!num.contains(temp2))
                System.out.println(temp2);
            else
            if(!num.contains(temp1))
                System.out.println(temp1);
        }
    }
}