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: Runtime Error)

x,_n = gets.chomp.split.map(&:to_i)
arr = gets.chomp.split.map(&:to_i)
#p "x:#{x}, n:#{n}, arr:#{arr}"

if arr == [] #空
  puts x
else
  unless arr.include?(x) #含まれない
    puts x 
  else
    s = ((0..100).to_a) - arr
    i = 0
    min = -1
    # 小さい
    while s[i] < x
      if min < s[i]
        min = s[i]
      end
      i += 1
    end

    # 大きい
    j = s.size - 1
    max = 101
    while s[j] > x
      if max > s[j]
        max = s[j]
      end
      j -= 1
    end
    if (max-x).abs < (x-min).abs
      puts max
    else
      puts min
    end
  end
end