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)

#include <bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#define ff first
#define ss second
#define pb push_back
#define eb emplace_back
#define pii pair<int, int>
#define pll pair<long long,long long>
#define vl vector<long long>
#define vll vector<pll>
#define vi vector<int>
#define vii vector<pii>
#define sws ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define endl '\n'
#define tcase int tt; cin>>tt; while(tt--)
#define tcase2 int tt; cin>>tt; for(int qq=1;qq<=tt;qq++)
using namespace std;
typedef long long int ll;
typedef  unsigned long long int ull;
typedef long double ld;
const int MAX = 1000010;
const int MOD2 = 998244353;
const int MOD = 1000000007; 
const int INF = 1e8;    
const ll LLINF = 0x3f3f3f3f3f3f3f3f;
const ld EPS = 1e-7;
// Extra
#define forn(i, n) for(int i = 0; i < (int)n; i++)
#define forne(i, a, b) for(int i = a; i <= b; i++)
#define all(x) x.begin(), x.end()   
#define trav(a, x) for(auto& a : x)
#define error(args...) { string _s = #args; replace(_s.begin(), _s.end(), ',', ' '); stringstream _ss(_s); istream_iterator<string> _it(_ss); err(_it, args); }
void err(istream_iterator<string> it) {}
template<typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
	cerr<< *it << " = " << a << endl;
	err(++it, args...);
}
using namespace __gnu_pbds;
template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
void solve()
{
    int x;
    cin>>x;
    int n;
    cin>>n;
    set<int> a;
    forn(i,n)
    {
        int p;
        cin>>p;
        a.insert(p);
    }
    int diff=INF;
    int ans=-1;
    for(int i=0;i<=101;i++)
    {
        if(a.find(i)==a.end() and diff>abs(i-x))
        {
            diff=abs(i-x);
            ans=i;
        }
    }
    cout<<ans<<endl;
}
int main()
{
    sws
    // tcase{
        solve();
    // }
    return 0;
}