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 <bits/stdc++.h>
#define fr first
#define se second
#define ll long long
#define pb push_back
using namespace std;
 
const ll INF = 1e16 + 1;
const ll N = 2e3 + 5;			
const ll mod = 1e9 + 7;
const long double eps = 1E-7;
 
int res;
int u[1001];
int main()
{
	int n, m, k;
	cin >> n >> m;
	map < int , int > mp;
	for ( int i=0; i<m; i++ ){
		cin >> k;
		mp[k] = true;
	}
	for ( int i=0; i<=100; i++ ){
		if ( mp[n - i] != true and n - i > 0 ){
			cout << n - i;
			return 0;
		}
		if ( mp[n + i] != true and n + i <= 100 ){
			cout << n + i;
			return 0;
		}
	}
}