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>
typedef long long     ll;
#define fast          ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define fr            first
#define sc            second
#define com(i,n)      for(int i=0;i<n;i++)
#define dom(i,n)      for(int i=1;i<=n;i++)
#define mom(i,n)      for(int i=n;i>=0;i--)
#define sortI(a,n)    sort(a,a+n)
#define sortD(a,n)    sort(a,a+n,greater<int>())
#define sortvi(a)     sort(a.begin(),a.end())
#define sortvd(a)     sort(a.begin(),a.end(),greater<int>())
#define sumall(a,x)   accumulate(a.begin(),a.end(),x)
#define pi            3.14159265358979323846264338327950
using namespace std;
map<ll,ll>mp;
int main()
{
    ll x,n,pos,con=1000,non=1000;
    cin>>x>>n;
    mp[x]++;
    if(n==0)
    {
        cout << x << endl;
        return 0;
    }
    com(i,n)
    {
        ll a;
        cin>>a;
        mp[a]=1;
    }
    for(int i=x+1; i<=100; i++)
    {
        if(mp[i]==0)
        {
            con=i-x;
            pos=i;
            break;
        }
    }
    for(int i=x-1; i>=0; i--)
    {
        if(mp[i]==0)
        {
            non=x-i;
            if(non<=con)
                pos=i;
            break;
        }
    }
    cout << pos << endl;
}