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: Runtime Error)


using System.Linq;
using System.Text;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Security.Cryptography.X509Certificates;
using System.Diagnostics;
using System.Reflection.Metadata;
using System.Threading;

namespace AtCoder
{
    class Program
    {

        struct Point
        {
            public int x;
            public int y;

            public Point(int x, int y)
            {

                this.x = x;
                this.y = y;

            }

        }


        const int BiggestMod = 1000000007;

        public static void Main()
        {

            var args = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();

            var x = args[0];
            var n = args[1];

            args = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();

            
            var ans = -100;
            var buf = Math.Abs(x - ans);

            foreach (var info in args)
                if (Math.Abs(x - info) < buf || (Math.Abs(x - info) == buf && info < buf))
                {
                    ans = info;
                    buf = Math.Abs(x - ans);
                }

            Console.WriteLine(ans);

        }

    }

}