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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.*;
import java.io.*;
public class Main
{
    public static void main(String args[])throws Exception
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw=new PrintWriter(System.out);
        String str[]=br.readLine().split(" ");
        int x=Integer.parseInt(str[0]);
        int n=Integer.parseInt(str[1]);
        TreeSet<Integer> ts=new TreeSet<>();
        for(int i=0;i<=101;i++)
        ts.add(i);
        str=br.readLine().split(" ");
        for(int i=0;i<n;i++)
        ts.remove(new Integer(Integer.parseInt(str[i])));
        int t1=ts.floor(x);
        int t2=ts.ceiling(x);
        if((int)Math.abs(t1-x)<(int)Math.abs(t2-x))
        pw.println(t1);
        else if((int)Math.abs(t1-x)>(int)Math.abs(t2-x))
        pw.println(t2);
        else
        pw.println(Math.min(t1,t2));
        pw.flush();
        pw.close();
    }
}