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)

getter = -> {
   require 'stringio'
  _in = StringIO.new
  while l = gets
    _in<< l
  end
  _in.string
}
s = getter.call.split(/\R/)
x,n = s[0].split(' ').map(&:to_i)
if n == 0
    _p = []
else
    *_p = s[1].split(' ').map(&:to_i)
end

def jdg(x, _p)
    return x if !_p.include?(x)
    right_check = ->{
        c = x + 1
        while _p.include?(c)
            c += 1
        end 
        [c - x , c]
    }.call

    left_check = ->{
        c = x - 1
        while _p.include?(c)
            c += 1
        end
        [x - c, c]
    }.call
    
    return left_check[1] if (left_check[0] <= right_check[0])
    right_check[1]
end

puts jdg(x, _p)