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 Ruby (2.7.1) (judge verdict: Wrong Answer)

# https://atcoder.jp/contests/abc170/tasks/abc170_c
#require 'pry'

X, N = gets.split.map(&:to_i)
if N == 0
  puts X
else
  ps = gets.split.map(&:to_i)
  min, max = ps.minmax

  s_min = min - 1 < 1 ? 1 : min - 1
  e_max = max + 1 > 100 ? 100 : max + 1

  ts = (s_min..e_max).to_a - ps

  abses = ts.map do |e|
    (e - X).abs
  end

  abses_min = abses.min

  min_count = abses.count(abses_min)

  #binding.pry

  min_index = abses.index(abses_min)

  ans = min_index ? ts[min_index] : X

  puts ans
end