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++ (Clang 10.0.0) (judge verdict: Wrong Answer)

#include <iostream>
#include <algorithm>
#include <cmath>
#include <queue>
#include <set>
#include <map>
#include <vector>
#include <string>
#include <iomanip>
#define faster       ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define f(i,a,b) for(ll i=a;i<b;i++)
#define r(i,a,b) for(ll i=a;i>b;i--)
using namespace std;
typedef long long ll;
typedef long double ld;


int main(){

ll x,n; cin>>x>>n;
vector <ll> v(n);
map <ll,ll> mp;

if(n==0){
  cout << x << endl;
  return 0;
}

f(i,0,n){
  cin>>v[i];
  mp[v[i]]++;
}

if(mp[x]==0){
  cout << x << endl;
  return 0;
}

ll ans1,ans2,num1=100,num2=100;

f(i,x,101){
  if(mp[i]==0){
    num1=abs(i-x);
    ans1=i;
    break;
  }
}

r(i,x,0){
  if(mp[i]==0){
    num2=abs(i-x);
    ans2=i;
    break;
  }
}

ll count=min(num1,num2);

if(count==num2){
  cout << ans2 << endl;
}else{
  cout << ans1 << endl;
}



}