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 xn =  scala.io.StdIn.readLine()
  val xnArray = xn.split(" ").map(_.toInt).toSeq
  val x = xnArray(0)
  val n = xnArray(1)

  val pInput =  scala.io.StdIn.readLine()

  if (n == 0) {
    println(x)
  } else {
    val pArray = pInput.split(" ").map(_.toInt).toVector.sorted
    if (pArray.find(_ == x).isEmpty) {
      println(x)
    } else {
      val min = pArray.head - 1
      val minSabun = Math.abs(x - min)
      val max = pArray.last + 1
      val maxSabun = Math.abs(x - max)

      var temp = -999
      var sabun = -999
      var result = -999
      if (minSabun > maxSabun) {
        sabun = maxSabun
        result = max
      } else {
        sabun = minSabun
        result = min
      }
      pArray.zipWithIndex.foreach { p =>
        if (temp == -999) {
          temp = p._1
        } else if (temp + 1 == p._1) {
          temp = p._1
        } else {
          // 現状より一つ前の値
          (temp + 1 to p._1 - 1).foreach { i =>
            val tempSabun = Math.abs(x - i)
            if (tempSabun < sabun) {
              sabun = tempSabun
              result = i
            } else if (tempSabun == sabun && i < result) {
              sabun = tempSabun
              result = i
            }
          }
          temp = p._1
        }
      }
      println(result)
    }
  }
}