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 C++ (GCC 9.2.1) (judge verdict: Accepted)

#include<iostream>
#include<vector>
#include<algorithm>
#include<stdlib.h>
#include<utility>
#include<functional>
#include<cfenv>
#include<cmath>
#include<string>
#include<queue>
#include<stack>
#include<map>
#include<set>

#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define vint vector<int>
#define vvint vector<vint>
#define P pair<ll,ll>
#define INT_MAX 2147483647
#define MOD 1000000007
#define PI 3.14159265358979323846
#define all(a) (a).begin(),(a).end()
using namespace std;
typedef long long ll;

#define MAX 1000000000000


int main(void) {
	int x, n; cin >> x >> n;
	map<int,int> mp;
	rep(i, n) {
		int y; cin >> y;
		mp[y]++;
	}
	
	for (int i = 0; i <= 100; i++) {
		if(mp[x-i]==0){
			cout << x - i << endl;
			break;
		}
		if (mp[x + i] == 0) {
			cout << x + i << endl;
			break;
		}
	}
	return 0;
}