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 REP(i,n) for (int i = 0; i < n; i++) 
using namespace std;
typedef long long ll;

int main() {
  
  int x, n;
  cin >> x >> n;
  
  vector<int> p(n);
  REP(i,n) {
    cin >> p[i];
  }

  
  int a, b, ia = 0, ib = 0, ans; 
  int c = 0;
  if (n == 0) cout << x << endl;
  else {
    int i = 0;
    while(1) {
      i++;
      a = x - i;
      REP(j,n) {
        if (a == p[j]) {
          ia++;
          break;
        }
      }
      if(ia == 0) {
        ans = a;
        c++;
        break;
      }
      else ia = 0;
      
      b = x + i;
      REP(k,n) {
        if (b == p[k]) {
          ib++;
          break;
        }
      }
      if(ib == 0) {
        ans = b;
        c++;
        break;
      }
      else ib = 0;
      
      if (c == 1) break;
    }
    cout << ans << endl;
  }
}