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)

using namespace std;
#include<string.h>
#include <sstream>
typedef long long int ll;
typedef long double ld;
#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <iterator>
#include <unordered_map>
#include <map>
//#define N 4
#include <stack>
#include <unordered_set>
#include <math.h>
#include <cstring>
#include <bitset>
#include <numeric>
#include <set>
#include <sstream>
#include <list>
#include <queue>
#define PI 3.14159265358979323846264338327950
#define mp make_pair
#define inf 1e9
//#define M 1000000007
#define M 10000000
#define N 100000

int p[110];
int main() {

	ios::sync_with_stdio(0);
	cin.tie(0);

	int x, n;
	cin >> x >> n;

	int a[n];

	int f = 0;
	for (int i = 0; i < n; i++) {
		cin >> a[i];

		p[a[i]] = 1;

		if (a[i] == x) {
			f = 1;
		}
	}

	if (f == 0) {
		cout << x << endl;
		return 0;
	}

	sort(a, a + n);

	int diff = 1e5;
	int ans = 0;

	for (int i = 0; i < 105; i++) {
		if (p[i] == 0) {

			if (abs(x - i) < diff) {
				diff = abs(x - i);
				ans = i;
			}
		}
	}

	cout << ans << endl;
}