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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
class c{
  public static void Main(){
    String[] str = Console.ReadLine().Split(' ');
    int x = int.Parse(str[0]);
    int n = int.Parse(str[1]);
    int ans;
    int dis = 1;
    if(n == 0){
      String s = Console.ReadLine();
      ans = x;
    }
    else{
      int[] num = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
      bool[] f = new bool[500];
      for(int i=0; i<n; i++){
        f[num[i]+250] = true;
      }
      while(true){
        if(!f[(x-dis)+150]){
          ans = x-dis;
          break;
        }
        if(!f[(x+dis)+150]){
          ans = x+dis;
          break;
        }
        dis++;
      }
    }
    Console.WriteLine(ans);
  }
}