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>
using namespace std;
using ll = long long;
using P  = pair <int, int>;

#define rep(i, n)     for (int i = 0; i < (int) (n); i++)
#define repr(i, a, b) for (int i = a; i < b; i++)
#define each(i, mp)   for (auto &i : mp)

const int INF = 1001001001;

int main()
{
  int x, n;
  cin >> x >> n;
  vector <int> p(n);
  rep(i, n) cin >> p[i];
  vector <int> elim_100(102);
  repr(i, 1, 101) {
    elim_100[i] = i;
    rep(j, n) {
      // std::cout << p[j] << '\n';
      if (i == p[j]) {
        elim_100[i] = 1000;
      }
    }
    // std::cout << elim_100[i] << '\n';
  }
  int dif_prv = INF;
  int dif     = 102;
  ll  ans     = 0;
  repr(i, 1, 101) {
    dif = abs(elim_100[i] - x);
    // std::cout << dif << '\n';
    if (dif_prv > dif) {
      ans     = i;
      dif_prv = dif;
    }
  }
  cout << ans << endl;

  return 0;
}