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 PHP (7.4.4) (judge verdict: Wrong Answer)

<?php

fscanf(STDIN,"%d %d",$x,$n);
$p=array_map('intval',explode(" ",fgets(STDIN)));
if($n==0){
    echo $x;
}else{
sort($p);
foreach(range(1,100) as $number){
    $arr[]=$number;
}
$result=array_diff($arr,$p);
$result=array_values($result);
$i=count($result)-1;
$j=$i;
$result[]=$x;
while($i>0){
    $k=$result[$i];
    if($result[$i+1]<$result[$i]){
        $result[$i]=$result[$i+1];
        $result[$i+1]=$k;
        $i--;
    }else{
        break;
    }
}
$key=array_search($x,$result);
if($key==0){
    $ans=$result[1];
}elseif($key==$j){
    $ans=$result[$j-1];
}elseif(abs($x-$result[$key-1])>abs($result[$key+1]-$x)){
    $ans=$result[$key+1];
}else{
    $ans=$result[$key-1];
}
echo $ans;
}