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;
//#define int long long
typedef pair<int,int> ii;
typedef tuple<int,int,int> iii;
#define ll long long
#define miniiPQ priority_queue<ii,vector<ii>,greater<ii> >
#define minPQ priority_queue<int,vector<int>,greater<int> >
#define PQ priority_queue<int>
#define iiPQ priority_queue<ii>
#define US unordered_set<int>
#define UMS unordered_multiset<int>
#define UM unordered_map<int>
#define ST stack<int>
 
void m1(){
  int x,n,k;
  cin >> x>>n;
  US us;
  for(int i=0;i<n;++i){
  	cin >> k;
    us.insert(k);
  }
  for(int i=0;i<=100;++i){
  	if(us.find(k-i) == us.end()){
    	cout << k-i;
      	return;
    }
    if(us.find(k+i) == us.end()){
    	cout << k+i;
      	return;
    }
  }
}
 
/*
void m2(){
  int t; cin >> t;
  while(t--) m1();
}
*/
 
int main(){
  //freopen("in.txt","r",stdin);
  m1();
  //m2();
}