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)

//e4 - e5 - f4
//#include <boost/multiprecision/cpp_int.hpp> 
#include "bits/stdc++.h"
#include "ext/pb_ds/assoc_container.hpp"
#include "ext/pb_ds/tree_policy.hpp"
typedef long long int ll;
typedef double db;
// __int128 s128;
// __uint128_t u128;
typedef unsigned long long u64;
#define int long long int
#define P 1000000007
#define Q 1000000006
#define sz(a) (ll)a.size()
#define lt(a) (ll)a.length()
#define pll pair<ll,ll>
#define f(i,a,b) for(ll i=(ll)a;i<(ll)b;i++)
#define bac(i,a,b) for(ll i=(ll)a;i>=(ll)b;i--)
#define mll map<ll,ll>
#define umll unordered_map<ll,ll>
#define vl vector<ll>
#define vvl vector<vector<ll>>
#define mt make_tuple
#define eb emplace_back
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define all(a) a.begin(),a.end()
#define F first
#define S second
#define teevra_gati ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define N 100005
#define PI 3.14159265359
#define inf LLONG_MAX
//using namespace boost::multiprecision; 
using namespace __gnu_pbds;
using namespace std;

void solve(){
    ll x,y1=200,y2=-1,n;
    cin>>x>>n;
    mll m;
    f(i,0,n){
        ll p;
        cin>>p;
        m[p]++;
    }
    f(i,x, x+150) if(m.count(i)==0){y1=i; break;}
    bac(i,x-1,x-150) if(m.count(i)==0){y2=i; break;}
    if(abs(y1-x) < abs(y2-x)) cout<<y1;
    else cout<<y2;
}

signed main() {
    teevra_gati
        
    solve();

    return 0;
}