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: Accepted)

#!/usr/bin/env ruby
x, n = gets.chomp.split(" ").map(&:to_i)
p = gets.chomp.split(" ").map(&:to_i)

p = p.sort

ans = 0

if p.empty?
  puts x
else
  0.upto(101) do |i|
    next if p.include?(i)

    if (x - i).abs < (x - ans).abs
      ans = i
    elsif (x - i).abs == (x - ans).abs && i < ans
      ans = i
    end
  end
  puts ans

  #
  # ans = x
  #
  # a = x
  # while a >= 0
  #   if !p.include?(a) && (x - a).abs <= (x - ans).abs && a < ans
  #     ans = a
  #     break
  #   end
  #   a -= 1
  # end
  #
  # if a == -1
  #   ans = x
  #   while p.include?(ans)
  #     ans += 1
  #   end
  # end
  #
  # puts ans
end