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++ (Clang 10.0.0) (judge verdict: Wrong Answer)

#include <iostream>
#include <vector>
#include <math.h>
#include <string>
#include <algorithm>
#include <functional>

using namespace std;

template <class T>
inline bool chmin(T &a, T b)
{
  if (a > b)
  {
    a = b;
    return true;
  }
  return false;
}
template <class T>
inline bool chmax(T &a, T b)
{
  if (a < b)
  {
    a = b;
    return true;
  }
  return false;
}

bool is_integer_modf(float x)
{
  float r;
  return 0 == modf(x, &r);
}

int main()
{
  int x, n;
  cin >> x >> n;
  int p[n];
  int d[101];
  int min = 1000;
  int min_num;

  for (int i = 0; i < 101; i++)
  {
    d[i] = 0;
  }

  for (int i = 0; i < n; i++)
  {
    cin >> p[i];
    d[p[i]] = 1;
  }

  sort(p, p + n);

  for (int i = 0; i < 101; i++)
  {
    if (d[i] == 0)
    {
      if (abs(i - x) < min)
      {
        min = abs(i - x);
        min_num = i;
      }
    }
  }

  cout << min_num;

  return 0;
}