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)

x, n = gets.chomp.split(' ').map{|i| i.to_i }
if n == 0
  puts x
  exit
end

pset = {}
pp = gets.chomp.split(' ').map{|i|
  ii = i.to_i
  pset[ii] = true
}

if pset[x].nil?
  puts x
else
  cursordiff = 1
  cursormax = x + cursordiff
  cursormin = x - cursordiff
  while pset[cursormax] && pset[cursormin]
    cursordiff += 1
    cursormax = x + cursordiff
    cursormin = x - cursordiff
  end

  if pset[cursormin].nil?
    puts cursormin
  else
    puts cursormax
  end
end