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.ArrayList;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        int X = s.nextInt();
        int N = s.nextInt();
        int P[] = new int[N];
        for (int i = 0; i < N; i++) {
            P[i] = s.nextInt();
        }
        int Q[] = new int[102];
        Arrays.sort(P);
        int p = 0;
        for (int i = 0; i <= 101; i++) {
            if (p < N) {
                if (P[p] == i) {
                    p++;
                } else {
                    Q[i] = i;
                }
            } else {
                Q[i] = i;
            }
        }
        int ans = 0;
        int d = 200;
        int d_tmp = 0;
        for (int i = 0; i <= 101; i++) {
            d_tmp = X - Q[i];
            if (d_tmp < 0) {
                d_tmp *= -1;
            }
            if (d > d_tmp) {
                d = d_tmp;
                ans = Q[i];
            }
        }
        System.out.println(ans);
        s.close();
    }
}