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.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main {

	public static void main(String[] args) {
		FastScanner sc = new FastScanner(System.in);

		int X = sc.nextInt();
		int N = sc.nextInt();

		if (N == 0) {
			System.out.println(X);
		}
		else {
			int[] numbers = new int[N];
			for (int i=0; i < N; i++) {
				numbers[i] = sc.nextInt();
			}

			int min = -1;
			for (int j=X; j >= 0; j--) {
				boolean found = false;
				for (int i=0; i < N; i++) {
					if (numbers[i] == j) {
						found = true;
						break;
					}
				}
				if (!found) {
					min = j;
					break;
				}
			}

			int max = -1;
			for (int j=X+1; j <= 101; j++) {
				boolean found = false;
				for (int i=0; i < N; i++) {
					if (numbers[i] == j) {
						found = true;
						break;
					}
				}
				if (!found) {
					max = j;
					break;
				}
			}

			if (max == -1 && min != -1) {
				System.out.println(min);
			}
			else if (min == -1 && max != -1) {
				System.out.println(max);
			}
			else {
				if ((X-min) <= (max-X)) {
					System.out.println(min);
				}
				else {
					System.out.println(max);
				}
			}
		}
	}

	private static class FastScanner {
		private BufferedReader reader = null;
		private StringTokenizer tokenizer = null;

		public FastScanner(InputStream in) {
			reader = new BufferedReader(new InputStreamReader(in));
			tokenizer = null;
		}

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

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

	}
}