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 <bits/stdc++.h>
#define rep(i, n) for(int i = 0; i < (n); i++)
using namespace std;
using P = pair<int, int>;
typedef long long ll;

signed main(void)
{
	int x, n, ans, mn;
	cin >> x >> n;
	vector<int> p(n);
	rep(i, n) cin >> p[i];
	ans = mn = 1e9;
	sort(p.begin(), p.end());
	for(int i = -1000; i <= 1000; i++)
	{
		bool ok = true;
		rep(j, n)
		{
			if (p[j] > i) 
				break;
			else if (p[j] == i)
				ok = false;
		}
		if (ok)
		{
			if (mn > abs(x - i))
			{
				mn = abs(x - i);
				ans = i;
			}
		}
	}
	cout << ans << endl;
	return 0;
}