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;

#define rep(i,n) for(int i=0; i<(int)(n); i++)

int main() {
    int X, N;
    cin >> X >> N;
    vector<int> Ps(N);
    rep(i, N) {
        cin >> Ps.at(i);
    }
    int i=0;
    bool found = false;
    while(!found){
        int tmp1 = X-i;
        int tmp2 = X+i;
        bool exist1 = false;
        bool exist2 = false;
        rep(j, N){
            if(Ps.at(j) == tmp1){
                exist1 = true;
            }
            if(Ps.at(j) == tmp2){
                exist2 = true;
            }
            if(exist1 && exist2){
                break;
            }
        }
        if(!exist1 && !exist2){
            found = true;
            cout << tmp1 << endl;
        } else if(!exist1 && exist2){
            found = true;
            cout << tmp1 << endl;
        } else if(exist1 && !exist2){
            found = true;
            cout << tmp2 << endl;
        }
        i++;
    }
}