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 1.8.0) (judge verdict: Accepted)

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		// 読み込み
		Scanner sc = new Scanner(System.in);
		int X = sc.nextInt();
		int N = sc.nextInt();

		List<Integer> p = new ArrayList<>();
		
		if (N == 0) {
			System.out.println(X);
			return;
		}
		for (int i = 1; i <=N ; i++) {
			p.add(sc.nextInt());
		}
		if (!p.contains(X)) {
			System.out.println(X);
			return;
		}
		
		int cost_l = Math.abs(X - 0);
		int ans_l = 0;
		
		for (int i = X -1; i >= 0 ; i--) {
			if(!p.contains(i)) {
				ans_l = i;
				cost_l = Math.abs(X - i);
				break;
			}
		}
		int cost_r = Math.abs(101 - X);
		int ans_r = 101;
		
		for (int i = X +1; i <= 101  ; i++) {
			if(!p.contains(i)) {
				ans_r = i;
				cost_r = Math.abs(X - i);
				break;
			}
		}		
		
		if(cost_l < cost_r) {
			System.out.println(ans_l);
		}
		else if(cost_l > cost_r) {
			System.out.println(ans_r);
		}
		else {
			System.out.println(ans_l);
		}
		
	}
}