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 proconio::input;

fn main() {
    input! {
        x: usize,
        n: usize,
        forbidden_list: [usize; n],
    }
    let mut vec = vec![(false, false); 100];

    for f in &forbidden_list {
        if x == *f {
            let diff = f - x;
            vec[diff] = (true, true);
        } else if x < *f {
            let diff = f - x;
            vec[diff].1 = true;
        } else {
            let diff = x - f;
            vec[diff].0 = true;
        }
    }

    for (i, v) in vec.iter().enumerate() {
        if !v.0 {
            println!("{}", x as isize - i as isize);
            break;
        } else if !v.1 {
            println!("{}", x+i);
            break;
        }
    }
}