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# (Mono-mcs 6.8.0.105) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
class Program
{
	static void Main(string[] args)
	{
		string[] str = Console.ReadLine().Split();
		int X = int.Parse(str[0]);
		int N = int.Parse(str[1]);
		int[]A = new int[N];
		if(N==0){
			Console.WriteLine(X);
		} else {
		string[] str2 = Console.ReadLine().Split();
		int[]B = new int[102];
		for(var i=0;i<N;i++){
			A[i] = int.Parse(str2[i]);
			B[A[i]]++;
		}
		int ans = 99999999;
		int min = 99999999;
		for(var i=0;i<102;i++){
			if(B[i]==0){
				int m = Math.Abs(X-i);
				if(m<min){
					ans = i;
					min = m;
				}
			}
		}
		Console.WriteLine(ans);
		}
	}
}