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 Scala (2.13.1) (judge verdict: Accepted)

object Main extends App {
    val Array(x, n) = io.StdIn.readLine.split(" ").map(_.toInt)
    
    if (n == 0) println(x)
    else {
        val ps = io.StdIn.readLine.split(" ").map(_.toInt)

        val ints = ((ps.min-1) to (ps.max+1)).toSet &~ ps.toSet

        def rec(diff: Int): Int = {
            if (ints.contains(x-diff)) x-diff
            else if (ints.contains(x+diff)) x+diff
            else rec(diff+1)
        }

        val result = rec(0)
        println(result)
    }
}