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)

#include <bits/stdc++.h>
using namespace std;

int main(){
  int X,N;
  cin >>X >>N;
  vector<int> P(N);
  vector<int> A(N);
  int sita=X;
  int ue=X;
  int answer=-1;
  int countsita=0;
  int countue=0;
  bool out=false;
  
  if(N==0){answer=X;}
  else{
    //Pを整頓
    for(int i=0; i<N; i++){cin >>P.at(i);}
    sort(P.begin(), P.end());
    //for(int i=0; i<N; i++){cout << P.at(i)<<" ";}cout<<endl;
    
    for(int j=0; j<N; j++){
      for(int i=0; i<N; i++){
        if(P.at(i) != sita){countsita++;}
        //cout << countsita << endl;
      	if(countsita>=N){out=true; break;}  
      }
      if(out){break;}
      
      countsita=0;
      sita--;
    }
    out=false;
    
    for(int j=0; j<N; j++){
      for(int i=0; i<N; i++){
        if(P.at(i) != ue){countue++;}
      	if(countue>=N){out=true; break;}  
      }
      if(out){break;}
      //cout << ue << endl;
      countue=0;
      ue++;
    }
    
    
    
    
    if(ue-X < X-sita){answer = ue;}
    else{answer = sita;}
    
    
  }
  
  cout<< answer <<endl;
}