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>
using namespace std;
 
int main(){
  
  int x,y;
  
  cin>>x>>y;
  
    int tmp = y - 2*x;
  
  if(tmp > 2*x){
    cout<<"No";
    return 0;
  
  }
  
  if(y%2 != 0){
    cout<<"No";
    return 0;
  }
  
  bool yes = false;
  
  if(x*2 > y){
    cout<<"No";
    return 0;
  }
  
    if(y/4 > x){
    cout<<"No";
    return 0;
  }
  

  
  for(int i = 0;i <= x;i++){
    int k = x-i;
    
    for(int j = 0;j <= k;j++){
      if(i*2 + j*4 == y){
        yes = true;
      }
    
    
    }
  
  }
  
  if(yes){
    cout<<"Yes";
  }else{
    cout<<"No";
  }
  
  
  
  return 0;
}