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: Accepted)

#include<iostream>
#include<vector>
#include<set>
#include<algorithm>
#include<cstring>
#include<string>
using namespace std;
#define MAX_N 100

int X,N;
set<int> p;

int main()
{
    int Answer;
    int x;
    cin >> X >> N;
    for(int i=0;i<N;i++){
        cin >> x;
        p.insert(x);
    }
    int i=0;
    while(1){
        if(p.find(X-i) == p.end()){
            Answer = X-i;
            cout << Answer;
            return 0;
        }else if(p.find(X+i) == p.end())
        {
            Answer = X+i;
            cout << Answer;
            return 0;
        }
        i++;
    }
}