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.split(' ').map(&:to_i)
p = gets.split(' ').map(&:to_i)
count = 0
plus = x
minus = x
minus_found = p.include?(x)
plus_found = p.include?(x)
if p.length == 0
    puts x
else
    if !minus_found
        puts x
    else
        while (minus_found && plus_found)
            plus +=1
            minus -= 1
            plus_found = p.include?(plus)
            minus_found = p.include?(minus)
            if plus_found == false || minus_found == false
                break
            end
        end
        if !plus_found && minus_found
            puts plus
        elsif plus_found  && !minus_found
            puts minus
        else
            puts (x- plus).abs < (x - minus).abs ? plus : minus
        end
    end
end