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: Accepted)

<?php
//$N = (int)trim(fgets(STDIN));
list($X,$N) = array_map('intval',explode(" ",trim(fgets(STDIN))));
//$S = trim(fgets(STDIN));
$p = array_map('intval',explode(" ",trim(fgets(STDIN))));

foreach($p as $v) {
  $key[$v]=1;
}

for($i=0;$i<200;$i++) {
  if (!isset($key[$X-$i])) {
    printf("%d\n",$X-$i);
    exit;
  }
  if (!isset($key[$X+$i])) {
    printf("%d\n",$X+$i);
    exit;
  }
}