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);
$array = explode(' ', trim(fgets(STDIN)));

if (!isset($array)) {
  echo $x;exit;
}

$nums = range(0, 100);
foreach ($array as $v) {
  unset($nums[$v]);
}

$array = array_values($nums);

$lef = -1;
$rig = count($array);

while ($rig - $lef > 1) {
  $mid = ceil($lef + ($rig - $lef) / 2);
  if ($array[$mid] > $x) {
    $rig = $mid;
  } else {
    $lef = $mid;
  }
}

if (!isset($array[$rig]) || abs($array[$lef] - $x) <= abs($array[$rig] - $x)) {
  echo $array[$lef];
} else {
  echo $array[$rig];
}