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 Kotlin (1.3.71) (judge verdict: Accepted)

import java.lang.Math.*

fun main(args: Array<String>) {
    val (x, n) = readListInt()
    if (n == 0) {
        println(x)
        return
    }
    val p = readListInt()

    val booleans = BooleanArray(102) {true}
    repeat(n) {
        booleans[p[it]] = false
    }
    var m = Int.MAX_VALUE
    var ans = Int.MAX_VALUE
    for (i in 0 until 102) {
        if (booleans[i]) {
            val d = abs(x - i)
            if (d < m) {
                ans = i
            }
            m = min(d, m)
        }
    }
    println(ans)
}

private fun read() = readLine()!!

private fun readInt() = read().toInt()

private fun readLong() = read().toLong()

private fun readDouble() = read().toDouble()

private fun readListString() = read().split(" ")

private fun readListInt() = readListString().map { it.toInt() }

private fun readListLong() = readListString().map { it.toLong() }

private fun readListDouble() = readListString().map { it.toDouble() }

private fun readMatrixString(n: Int): List<List<String>> {
    val matrix = mutableListOf<List<String>>()
    for (i in 0 until n) {
        val list = readListString()
        matrix.add(list)
    }
    return matrix
}

private fun readMatrixInt(n: Int): List<List<Int>> {
    val matrix = mutableListOf<List<Int>>()
    for (i in 0 until n) {
        val list = readListInt()
        matrix.add(list)
    }
    return matrix
}

private fun readMatrixDouble(n: Int): List<List<Double>> {
    val matrix = mutableListOf<List<Double>>()
    for (i in 0 until n) {
        val list = readListDouble()
        matrix.add(list)
    }
    return matrix
}

private fun readMatrixLong(n: Int): List<List<Long>> {
    val matrix = mutableListOf<List<Long>>()
    for (i in 0 until n) {
        val list = readListLong()
        matrix.add(list)
    }
    return matrix
}