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(void) {
    int x, n;
    cin >> x >> n;
    int p;
    bool pn[102];
    for (int i = 0; i < 101; i++) {
        pn[i] = true;
    }
    for (int i = 0; i < n; i++) {
        cin >> p;
        pn[p] = false;
    }
    if (n == 0) {
        cout << x << endl;
        return 0;
    }

    // 入力されたpiがpn[pi] = falseとなっている
    int ans = 0;
    int count = 0;
    while (ans == 0) {
        int shita = x - count;
        if (shita >= 1) {
            if (pn[shita] == true) {
                ans = shita;
                break;
            }
        }
        int ue = x + count;
        if (ue <= 101) {
            if (pn[ue] == true) {
                ans = ue;
                break;
            }
        }
        count++;
        if (count > 100) {
            break;
        }
    }
    cout << ans << endl;
}