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: Wrong Answer)

use std::cmp;
fn main(){
    let (x, _n) = {
        let mut s = String::new();
        std::io::stdin().read_line(&mut s).unwrap();
        let mut ws = s.split_whitespace();
        let x: i32 = ws.next().unwrap().parse().unwrap();
        let n: i32 = ws.next().unwrap().parse().unwrap();
        (x, n)
    };
    let mut vec: Vec<i32> = Vec::new();

    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    let ws = s.split_whitespace();

    for v in ws {
        let t: i32 = v.parse().unwrap();
        vec.push(t);
    }

    let mut i = 0;
    loop {
        let mut flag_a = false;
        let mut flag_b = false;
        let mut ans_a: i32 = 0;
        let mut ans_b: i32 = 0;

        let t1 = x + i;
        if !vec.contains(&t1) {
            ans_a = t1.abs();
            flag_a = true;
        }

        let t2 = x - i;
        if !vec.contains(&t2) {
            ans_b = t2.abs();
            flag_b = true;
        }

        if flag_a && !flag_b {
            println!("{}", ans_a);
            return
        } else if !flag_a && flag_b {
            println!("{}", ans_a);
            return
        } else if flag_a && flag_b {
            println!("{}", cmp::min(ans_a, ans_b));
            return
        }
        i += 1;
    }
}