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)

line = gets.split(' ')
x = line[0].to_i
n = line[1].to_i

if n == 0 then
  p x
  return
end

pline = gets.split(' ')
nline = []
pline.each do |p|
  nline << p.to_i
end
nline.push x
nline.sort!.uniq!

a = ((nline[0]-1)..nline[nline.size - 1]).to_a

dist = a - nline
if dist.size == 0 then
  dist = nline
end
dist.push(x).sort!.uniq!
index = dist.index(x)
p dist

if index == (dist.size-1) then
  dist.push x+1
end
left = dist[index] - dist[index-1]
right = dist[index+1] - dist[index]
answer = left <= right ? dist[index-1] : dist[index+1]
p answer