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;
class Program
 {
   	static void Main(string[] args)
        {
    　　	string a = Console.ReadLine(); //標準入力
		string[] aa = a.Split(' ');
		
	       	int X = int.Parse(aa[0]);
       		int N = int.Parse(aa[1]);
		string b = Console.ReadLine(); //標準入力
		string[] bb = b.Split(' ');
		
		int[] cc = new int[bb.Length];
		for(int i = 0; i< cc.Length; i++){
      			cc[i]= int.Parse(bb[i]);
      	}	
		
		
  		int count = 101;
		for(int i = -2; i< 101; i++){
          bool test = false;
          		for(int j = 0; j< cc.Length; j++){
      			test = test || i == cc[j];
      			}
          		if(!test){
      				int abs = (int) (Math.Abs(i-X));
                  	if(count>abs){
                      count = abs;
                    }
                }
      	}
     		Console.WriteLine("{0}", count);
        }
 
  	
	static void changev(int h){
    
  	}
 }