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 Rust (1.42.0) (judge verdict: Accepted)

use std::io::*;

fn contains(v: &Vec<i32>, num: i32)-> bool {
    v.iter().any(|&i| i==num)
}

fn main() {
    let mut buf = String::new();
    stdin().read_line(&mut buf).unwrap();
    let nums: Vec<i32> = buf.split_whitespace().map(|n| n.parse().unwrap()).collect::<Vec<i32>>();

    let x = nums[0];
    let n = nums[1];

    let mut buf = String::new();
    stdin().read_line(&mut buf).unwrap();
    let mut nums: Vec<i32> = buf.split_whitespace().map(|n| n.parse().unwrap()).collect::<Vec<i32>>();

    nums.sort_by(|x, y| x.cmp(y).reverse());

    if nums.len() == 0 {
        let out = stdout();
        let mut out = out.lock();
        writeln!(out, "{}\n", x).unwrap();
        return;
    }

    let mut p = x;
    let mut less = 0;
    loop {
        if !contains(&nums, p) {
            less = p;
            break;
        }
        p -= 1;
    }

    let mut p = x;
    let mut more = 0;
    loop {
        if !contains(&nums, p) {
            more = p;
            break;
        }
        p += 1;
    }

    if x - less <=  -(x - more) {
        let out = stdout();
        let mut out = out.lock();
        writeln!(out, "{}\n", less).unwrap();
    } else {
        let out = stdout();
        let mut out = out.lock();
        writeln!(out, "{}\n", more).unwrap();
    }
}