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.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int x = sc.nextInt();
		int n = sc.nextInt();
		int[] ps = new int[n];
		int[] hantei = new int[101];
		for(int i=0; i<n; i++){
			ps[i] = sc.nextInt();
			hantei[ps[i]] = 1;
		}
		int ans1 = 1000;
		for(int i=x; i<=101; i++){
			if(i == 101) {
				ans1 = 101;
				break;
			}
			if(hantei[i] == 0){
				ans1 = i;
				break;
			}
		}
		int ans2 = 1000;
		for(int i=x; i>=-1; i--){
			if(i == 0) {
				ans2 = 0;
				break;
			}
			if(hantei[i] == 0){
				ans2 = i;
				break;
			}
		}
		if((ans1-x)<(x-ans2)){
			System.out.println(ans1);
		} else {
			System.out.println(ans2);
		}
	}
}