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: Wrong Answer)

#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <string>
using namespace std;
typedef long long int ll;
typedef vector<int> vi;
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define Sort(a) sort(a.begin(), a.end())
const int INF = 1<<30;
const ll MOD = 1000000007;

int main(void) {

    int x, n;
    cin >> x >> n;
    vector<bool> v(101, false);
    rep(i, n){
        int num;
        cin >> num;
        v[num] = true;
    }

    rep(i, 50) {
        if (v[x-i] == false) {
            cout << x-i << endl;
            return 0;
        }
        if (v[x+i] == false) {
            cout << x+i << endl;
            return 0;
        }
    }


    return 0;
}