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<iostream>
#include<cmath>
#include<string>
#include<string.h>
#include<algorithm>
#include<vector>
#include<map>
#include<queue>
#include<stack>
#include<set>
#include<climits>
#include<deque>
#include<iomanip>
using namespace std;
#define int                  long long
#define double               long double
#define ass_on_fire          ios_base::sync_with_stdio(false);cin.tie(0);
#define vi                   vector<int>
#define di                   deque<int>
#define si                   set<int>
#define vpii                 vector<pair<int,int>>
#define pi                   pair<int,int>
#define pub                  push_back
#define puf                  push_front
#define pob                  pop_back
#define pof                  pop_front
#define all(a)               a.begin(),a.end()
#define rall(a)              a.rbegin(),a.rend()
#define PI                   3.1415926535897932384626433832795
#define read(a)              for(auto& x:a) cin>>x
#define endl                 '\n'
#define ln                   printf("\n");
#define gap                  ' '
#define min3(a,b,c)          min(a, min(b, c))
#define max3(a,b,c)          max(a, max(b, c))
#define MOD                  1000000007
//freopen("input.txt","r",stdin);
//freopen("output.txt","w",stdout);
int32_t main()
{
    ass_on_fire
    int q,n;cin>>q>>n;
    set<int>s;
    for(int i=0;i<100;i++) s.insert(i+1);
    for(int i=0,x;i<n;i++) cin>>x,s.erase(s.find(x));
    int ans=INT_MAX,best=q;
    for(auto x:s)
    {
        if(abs(x-q)<ans)
        {
            best=x;
            ans=abs(q-x);
        }
        if(abs(x-q)==ans)
        {
            best=min(best,x);
        }
    }
    cout<<best;
}