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 main() {
        var n, x int
        fmt.Scan(&x, &n)
        if n == 0 {
                fmt.Println(x)
                return
        }
        s := make([]int, n)
        for i := 0; i < n; i++ {
                fmt.Scan(&s[i])
        }
        var i = 0
        for {
                if !contains(s, x-i) {
                        fmt.Printf("%v", x-i)
                        return
                }
                if !contains(s, x+i) {
                        fmt.Printf("%v", x+i)
                        return
                }
          i++
        }
        return
}

func contains(s []int, i int) bool {
        for _, item := range s {
                if item == i {
                        return true
                }
        }
        return false
}