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 OCaml (4.10.0) (judge verdict: Accepted)

open Batteries
let x, n = Scanf.sscanf (read_line()) "%d %d" (fun  x n-> x ,n)
let p_ = read_line ()
let p = (if p_ = "" then [] else p_ |> String.split_on_char ' ' |> List.map int_of_string)
let rec loop i =
  if List.mem (x - i) p then 
  if List.mem (x + i) p then (loop (i+1))
  else (x + i)
  else (x - i)
let _ = Printf.printf "%d\n" @@ loop 0