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();

        if(n == 0) {
            System.out.println(x);
            System.exit(0);
        }

        int[] p = new int[102];
        boolean[] isGivenNum = new boolean[102];
        boolean isXMatched = false;
        int xIndex = 0;

        for(int i=0; i<n; i++) {
            int tmp = sc.nextInt();
            p[tmp] = Math.abs(x-tmp);
            isGivenNum[tmp] = true;
            if(tmp == x) {
                xIndex = tmp;
                isXMatched = true;
            }
        }

        System.out.println("xIndex" + xIndex);

        if(!isXMatched) {
            System.out.println(x);
            System.exit(0);
        }

        int fIndex = 101;
        int fDistance = 0;
        for(int i=xIndex; i<p.length; i++) {
            if(isGivenNum[i] == false) {
                fIndex = i;
                fDistance = i - xIndex;
                break;
            }
        }

        int bIndex = 0;
        int bDistance = 0;
        for(int i=xIndex; i>=0; i--) {
            if(isGivenNum[i] == false) {
                bIndex = i;
                bDistance = xIndex - i;
                break;
            }
        }

        if(fIndex == 101) {
            System.out.println(fIndex);
        } else if(bIndex == 0) {
            System.out.println(bIndex);
        } else {
            if(fDistance == bDistance) {
                System.out.println(Math.min(bIndex, fIndex));
            } else if(fDistance > bDistance) {
                System.out.println(bIndex);
            } else {
                System.out.println(fIndex);
            }
        }
    }
}