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;
using System.Linq;
using System.Collections.Generic;

namespace ConsoleApp1 {
    public class Class {
        static void Main(string[] args) {
            var XN = RL<int>();
            if(XN[1] == 0) {
                Console.Write(XN[0]);
                return;
            }
            var A = RL<int>();
            var t = new int[101];
            for (var i = 0; i < XN[1]; i++) {
                t[A[i] - 1]--; 
            }
            var ans = 101;
            for (var i = 0; i < t.Length; i++) {
                if(t[i] == 0) {
                    if (Math.Abs(XN[0] - (i + 1)) < Math.Abs(XN[0] - (ans + 1))) {
                        ans = i;
                    }
                }
            }
            if(ans == 101) {
                Console.Write(XN[0]);
                return;
            }
            Console.Write(ans + 1);
        }

        static T[] RL<T>() where T : IComparable {
            if (typeof(T) == typeof(int)) {
                return (T[])(object)Console.ReadLine().Trim().Split().Select(int.Parse).ToArray();
            }
            if (typeof(T) == typeof(long)) {
                return (T[])(object)Console.ReadLine().Trim().Split().Select(long.Parse).ToArray();
            }
            if (typeof(T) == typeof(double)) {
                return (T[])(object)Console.ReadLine().Trim().Split().Select(double.Parse).ToArray();
            }
            if (typeof(T) == typeof(decimal)) {
                return (T[])(object)Console.ReadLine().Trim().Split().Select(decimal.Parse).ToArray();
            }
            return (T[])(object)Console.ReadLine().Trim().Split().ToArray();
        }
    }
}