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.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.StringTokenizer;

/**
 * Built using CHelper plug-in Actual solution is at the top
 */
public class Main {
	public static void main(String[] args) {
		InputReader in = new InputReader(System.in);
		PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)), true);
		TaskB solver = new TaskB();
		solver.solve(1, in, out);
		out.flush();
		out.close();
	}
}

class Pair {
	int first;
	int second;

	Pair(int first, int second) {
		this.first = first;
		this.second = second;
	}
}

class TaskB {

	public void solve(int testNumber, InputReader in, PrintWriter pw) {
		int X = in.nextInt();
		int N = in.nextInt();
		boolean arr[] = new boolean[102];
		Arrays.fill(arr, true);
//		ArrayList<Integer> ans=new ArrayList<Integer>();
		int num[] = new int[N];
		for (int i = 0; i < N; i++) {
			num[i] = in.nextInt();
			arr[num[i]] = false;
		}
		int min = Integer.MAX_VALUE;
		int index = -1;
		for (int i = 0; i <= X; i++) {
			if (arr[i]) {
				int temp = Math.abs(X - i);
				if (temp < min) {
					index = i;
					min = temp;
				}

			}
		}
		for (int i = X + 1; i <= 101; i++) {
			if (arr[i]) {
				int temp = Math.abs(X - i);
				if (temp < min) {
					index = i;
					min = temp;
				}

			}
		}
		pw.println(index);

	}

	long __gcd(long a, long b) {
		if (b == 0)
			return a;
		return __gcd(b, a % b);

	}

	public int getInt(int num) {
		int ret = -1;
		switch (num) {
		case 0:
			ret = 6;
			break;
		case 1:
			ret = 2;
			break;
		case 2:
			ret = 5;
			break;
		case 3:
			ret = 5;
			break;
		case 4:
			ret = 4;
			break;
		case 5:
			ret = 5;
			break;
		case 6:
			ret = 6;
			break;
		case 7:
			ret = 3;
			break;
		case 8:
			ret = 7;
			break;
		case 9:
			ret = 6;
			break;
		}
		return ret;
	}

	public int isPow(long num) {
		int count = 0;
		while (num > 0) {
			num /= 2;
			count++;
		}
		return count;
	}
}

class InputReader {
	BufferedReader br;
	StringTokenizer st;

	public InputReader(InputStream in) {
		br = new BufferedReader(new InputStreamReader(in));
		st = null;
	}

	public String next() {
		while (st == null || !st.hasMoreTokens()) {
			try {
				st = new StringTokenizer(br.readLine());
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
		}
		return st.nextToken();
	}

	public int nextInt() {
		return Integer.parseInt(next());
	}

	public long nextLong() {
		return Long.parseLong(next());
	}

	public double nextDouble() {
		return Double.parseDouble(next());
	}
}