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: Wrong Answer)

package main

import (
	"fmt"
	"os"
)

func abs(x int) int {
	if x < 0 {
		return x * (-1)
	}
	return x
}
func main() {
	var x, n, t int
	fmt.Scan(&x, &n)
	if n == 0 {
		fmt.Println(x)
		os.Exit(0)
	}
	mp := make(map[int]int)
	for i := 0; i < n; i++ {
		fmt.Scan(&t)
		mp[t] = 1
	}
	res := 101
	an := 0
	for i := 1; i < 102; i++ {
		if abs(int(x-i)) < res && mp[i] == 0 {
			an = i
			res = x - i
		}
	}
	fmt.Println(an)
}