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)

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    s.trim_end().split_whitespace().map(|e| e.parse().ok().unwrap()).collect()
}

fn invec(v: &Vec<i16>, x: i16) -> bool {
    for i in v {
        if i == &x {
            return true
        }
    }
    false
}
fn main() {
    let v: Vec<i16> = read_vec();
    let p: Vec<i16> = read_vec();
    let x = v[0];
    //let n = v[1];
    for i in 0..100 {
        if !invec(&p, x - i) {
            println!("{}", x - i);
            return
        }
        if !invec(&p, x + i) {
            println!("{}", x + i);
            return
        }
    }
}