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)

fn main() {
    let (x, n, ps) = read();
    let ans = solve(x, n, ps);
    write(ans);
}

fn read() -> (i32, i32, Vec<i32>) {
    let mut l1 = String::new();
    std::io::stdin().read_line(&mut l1).ok();
    let mut iter1 = l1.trim().split_whitespace();
    let x = iter1.next().unwrap().parse::<i32>().unwrap();
    let n = iter1.next().unwrap().parse::<i32>().unwrap();

    let mut l2 = String::new();
    std::io::stdin().read_line(&mut l2).ok();
    let mut v: Vec<i32> = l2.trim().split_whitespace().map(|x| x.parse::<i32>().unwrap()).collect();
    v.sort();

    (x, n, v)
}

fn write(ans: i32) {
    println!("{}", ans);
}

fn solve(x: i32, n: i32, ps: Vec<i32>) -> i32 {
    let mut distance = 0;
    let mut i = x;
    let mut j = x;
    loop {

        if let None = ps.iter().find(|&&e| e == i) {
            break i;
        } 
        if let None = ps.iter().find(|&&e| e == j)  {
            break j;
        } 
        distance += 1;
        if i > 1 {
            i -= distance;   
        }
        if j < 100 {
            j += distance;
        }
    }
}