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;
 
typedef long long int ll;
typedef long double ld;
 
//****************************************************                
#define f(var,start,end) for(ll var = start; var <end ; ++var)
#define rf(var,start,end) for(ll var = start; var>=end ; var--)
#define pb push_back
#define mp make_pair
#define pf push_front
#define vvll vector<vector<ll>>
#define mtp make_tuple
#define ff first
#define ss second
#define vll vector<ll>
#define pll pair<ll,ll> 
#define vpll vector<pll>
#define all(X) X.begin(),X.end()
#define nl cout<<"\n"
#define trace1(a) cerr << #a << ": " << a << endl;
#define trace2(a,b) cerr << #a << ": " << a << " " << #b << ": " << b << endl;
#define trace3(a,b,c) cerr << #a << ": " << a << " " << #b << ": " << b << " " << #c << ": " << c << endl;
#define trace4(a,b,c,d) cerr << #a << ": " << a << " " << #b << ": " << b << " " << #c << ": " << c << #d << ": " << d << endl;
#define OC freopen("input.txt" , "r", stdin); freopen("output.txt" , "w", stdout) 
#define MOD (ll)1e9+7; //change it for other mods
#define FAST_IO ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)
        //*******************************************************
//Some Functions
void solve();

int binary(int a[],int l,int r,int find)
{
    if(l>r)
    {
        return -1; 
    }else
    {
        int mid=(l+r)/2;
        if(a[mid]==find)
        {
            return mid+1;
        }else if(a[mid]>find)
        {
            binary(a,l,mid-1,find);
        }else
        {
            binary(a,mid+1,r,find);
        }   
    }   
    return 0;
}

int main()
{
    FAST_IO;
    ll testcases = 1;
    // cin >> testcases; //comment for 1 test case
    while(testcases--)
    {
        solve();
    }
    return 0;
}

void solve()
{
	ll k,n;
	cin>>k>>n;
	vll a(n);
	vll mp(101,0);
	f(x,0,n)
	{
		cin>>a[x];
		mp[a[x]]++;
	}
	ll ans=0;
	ll mn=k;
	f(x,0,101)
	{
		if(mp[x]==0)
		{
			ll vl=abs(k-x);
			if(vl<mn)
			{
				mn=vl;
				ans=x;
			}
		}
	}
	cout<<ans;
	nl;
}