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::cmp;
use std::fmt::Debug;
use std::str::FromStr;
#[allow(dead_code)]
fn read_as_vec<T>() -> Vec<T>
where
    T: FromStr,
    <T as FromStr>::Err: Debug,
{
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    s.trim()
        .split_whitespace()
        .map(|c| T::from_str(c).unwrap())
        .collect()
}

#[allow(dead_code)]
fn read_as_string() -> String {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    s.trim().to_string()
}

fn main() {
    let line = read_as_vec::<usize>();
    let (x, n) = (line[0], line[1]);
    let p = read_as_vec::<usize>();
    if !p.contains(&x) {
        println!("{}", x);
        return;
    }
    let mut ans = 0;
    for i in 0..=101 {
        if !p.contains(&i) && (i as i64 - x as i64).abs() < (ans - x as i64).abs() {
            ans = i as i64;
        }
    }
    println!("{}", ans);
    // let mut are_included: Vec<bool> = vec![false; 250];
    // for elem in p {
    //     are_included[elem + 125] = true;
    // }
    // let mut ans: i64 = 0;
    // for i in 0..250 {
    //     if are_included[i] {
    //         continue;
    //     }
    //     let i = i as i64 - 125;
    //     let x = x as i64;
    //     if (i - x as i64).abs() <= (x - ans).abs() && x < ans {
    //         ans = i;
    //     }
    // }
    //println!("{}", ans);
}