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)


function main(input) {
    let [X, N, ...ps] = input.trim().split(/[\s\n]/).map(Number)
    
    let down = X
    let up = X

    let changed = false
    do {
        changed = false
        for(const p of ps) {
            if(down === p) {
                down--
                changed = true
            }

            if(up === p) {
                up++
                changed = true
            }
        }
    } while(changed)

    const d = Math.abs(down - X)
    const u = Math.abs(up - X)
    
    if(d === u || d < u) {
        console.log(down)
    } else {
        console.log(up)
    }
}

main(require("fs").readFileSync("/dev/stdin", "utf8"))