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"

func main() {
	var x, n int
	fmt.Scan(&x, &n)

	list := make([]int, n)
	for i := 0; i < n; i++ {
		fmt.Scan(&list[i])
	}
	if n == 0 {
		fmt.Println(x)
		return
	}

	min := 0
	diff := 100
	for i := x - 1; i >= 0; i-- {
		flag := false
		for j := 0; j < n; j++ {
			if i == list[j] {
				flag = true
			}
		}
		if !flag && x-min > x-i {
			min = i
			diff = x - i
		}
	}
	min2 := 100
	diff2 := 100
	for i := x + 1; i <= 101; i++ {
		flag := false
		for j := 0; j < n; j++ {
			if i == list[j] {
				flag = true
			}
		}
		if !flag && min2-x > i-x {
			min2 = i
			diff2 = i - x
		}
	}
	if diff > diff2 {
		fmt.Println(min2)
	} else if diff < diff2 {
		fmt.Println(min)
	} else {
		fmt.Println(min)
	}
}