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>
using namespace std;
#define endl "\n"
#define int long long
 
const int N = 1e5 + 5;
 
int x, n;
int a[N];
 
int32_t main()
{
    cin >> x >> n;
    for(int i = 1; i <= n; i++)
        cin >> a[i];
    for(int off = 0; ;off++)
    {
        int val = x - off;
        int flag = 1;
        for(int i = 1; i <= n; i++)
            flag &= (a[i] != val);
        if(flag)
        {
            cout << val;
            return 0;
        }
        val = x + off;
        flag = 1;
        for(int i = 1; i <= n; i++)
            flag &= (a[i] != val);
        if(flag)
        {
            cout << val;
            return 0;
        }
    }
    return 0;
}