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;
use std::vec::Vec;

fn find(x: isize, p: &[isize]) -> bool {
  for v in p.iter() {
    if *v == x {
      return true;
    }
  }
  false
}

fn main() {
  input! {
    x: isize,
    n: usize,
    mut p: [isize;n],
  }
  p.sort();
  let mut last = 0_isize;
  let mut diff = 10000_isize;
  for i in 0_isize..102_isize {
    if find(i, &p) {
      continue;
    }
    let d = (i - x).abs();
    if d >= diff {
      break;
    }
    diff = d;
    last = i;
  }
  println!("{}", last);
}