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 JavaScript (Node.js 12.16.1) (judge verdict: Accepted)

const fs = require('fs')
const inputs = fs.readFileSync('/dev/stdin', 'utf8').trim().split(/\s+/).map(s => parseInt(s))

const x = inputs[0]
const n = inputs[1]
const pSet = new Set()

inputs.slice(2, n + 2).forEach(p => pSet.add(p))

let diff = 0
while (true) {
  if (!pSet.has(x - diff)) {
    console.log(x - diff)
    break;
  }
  if (!pSet.has(x + diff)) {
    console.log(x + diff)
    break;
  }
  diff += 1
}