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 1.8.0) (judge verdict: Accepted)

import java.io.*;
import java.util.*;
 
public class Main{
    static class FastReader{
        BufferedReader br; 
        StringTokenizer st; 
        public FastReader(){br = new BufferedReader(new InputStreamReader(System.in));} 
        String next(){while (st == null || !st.hasMoreElements()){try{st = new StringTokenizer(br.readLine());}catch (IOException  e){e.printStackTrace();}}return st.nextToken();} 
        int nextInt(){return Integer.parseInt(next());} 
        long nextLong(){return Long.parseLong(next());} 
        double nextDouble(){return Double.parseDouble(next());} 
        int[] readArray(int n){int[] a=new int[n];for (int i=0; i<n; i++) a[i]=nextInt();return a;}
        long[] readLongArray(int n){long[] a=new long[n];for (int i=0; i<n; i++) a[i]=nextLong();return a;}
        String nextLine(){String str = "";try{str = br.readLine();}catch (IOException e){e.printStackTrace();}return str;} 
    }
    static int getgcd(int n1,int n2){
        while(n1 != n2){
            if(n1 > n2) n1 -= n2;
            else n2 -= n1;
        }
        return n1;
    }
    static boolean isSorted(int[] arr, int n){
        for(int i=1;i<n;i++){
            if(arr[i]<arr[i-1]) return false;
        }
        return true;
    }
    static boolean isPrime(long n){
        if(n==2) return true;
        else if(n%2==0) return false;
        for(int i=3;i<=n/2;i+=2){
            if(n%i==0) return false;
        }
        return true;
    }
    static void printArray(int[] arr){
        for(int x:arr){
            System.out.print(x+" ");
        }
        System.out.println();
    }
    public static void main(String[] args) throws NumberFormatException, IOException {
        FastReader s=new FastReader(); 
        int x=s.nextInt();int n=s.nextInt();
        HashSet<Integer> hs = new HashSet<>();
        for(int i=0;i<n;i++){
            hs.add(s.nextInt());
        }
        boolean test = true;
        if(!hs.contains(x)) System.out.println(x);
        else{
            int i=x,j=x;
            while(test){
                if(!hs.contains(--i)){
                    System.out.println(i);test=false;break;
                }else if(!hs.contains(++j)){
                    System.out.println(j);test=false;break;
                }
            }
        }

    }
}