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 C# (.NET Core 3.1.201) (judge verdict: Wrong Answer)

using System;

namespace AtCoder{
    public static class AtCoder{
        public static void Main(){
            var input = Console.ReadLine().Split(' ');
            int x = int.Parse(input[0]);
            int n = int.Parse(input[1]);

            var line = Console.ReadLine().Split(' ');
            var nums = new int[102];
            for(int i = 0; i < n; i++){
                nums[int.Parse(line[i])] = 1;
            }

            for(int i = 0; i <= 101; i++){
                if((x - i >= 0) && (nums[x - i] == 0)){
                    Console.WriteLine(x - i);
                    return;
                }
                if((x + i <= 100) && (nums[x + i] == 0)){
                    Console.WriteLine(x + i);
                    return;
                }
            }
            Console.WriteLine("0");
        }
    }
}