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 Go (1.14.1) (judge verdict: Accepted)

package main

import "fmt"

func abs(x int) int {
	if x < 0 {
		return -x
	}
	return x
}

func main() {
	var x, n int
	fmt.Scan(&x, &n)
	num := make([]int, n)
	for i := 0; i < n; i++ {
		fmt.Scan(&num[i])
	}

	p := map[int]bool{}
	for i := 0; i < n; i++ {
		p[num[i]] = true
	}
	ans := -100
	for i := 0; i <= 101; i++ {
		if p[i] {
			continue
		}
		if abs(x-i) < abs(x-ans) {
			ans = i
		}
	}
	fmt.Println(ans)
}