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)

#define _GLIBCXX_DEBUG //提出時にはこれは消す
#include <bits/stdc++.h>
using namespace std;
int main(){
  int x,n, flag;
  cin >> x >> n;
  int p[n];
  for(int i=0; i<n; i++)
    cin >> p[i];
  sort(p, p+n);
  int ct=0;
  while(1){
    flag = 0;
    for(int i=0; i<n; i++){
      if(x-ct==p[i]){
	flag = 1;
	break;
      }
    }
    if(flag==0){
      cout << x-ct;
      return 0;
    }
    flag = 0;
    for(int i=0; i<n; i++){
      if(x+ct==p[i]){
	flag = 1;
	break;
      }
    }
    if(flag==0){
      cout << x+ct;
      return 0;
    }
    ct++;
  }
  return 0;
}