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 (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func lib_CountInt(values []int) map[int]int {
	m := map[int]int{}
	for _, value := range values {
		m[value]++
	}
	return m
}
func main() {
	scanner := bufio.NewScanner(os.Stdin)
	const initialBufSize = 4096
	const maxBufSize = 1000000
	scanner.Buffer(make([]byte, initialBufSize), maxBufSize)
	scanner.Split(bufio.ScanWords)
	var X int
	scanner.Scan()
	X, _ = strconv.Atoi(scanner.Text())
	var N int
	scanner.Scan()
	N, _ = strconv.Atoi(scanner.Text())
	p := make([]int, N)
	for i := 0; i < N; i++ {
		scanner.Scan()
		p[i], _ = strconv.Atoi(scanner.Text())
	}
	fmt.Println(solve(X, N, p))
}
func solve(X int, N int, p []int) int {
	counts := lib_CountInt(p)
	for i := 0; ; i++ {
		if _, ok := counts[X-i]; !ok {
			return X - i
		}
		if _, ok := counts[X+i]; !ok {
			return X + i
		}
	}
}