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 <stdio.h>

#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>

#define N 200010
#define MAX 1000000000000000000
#define MOD 1000000007

#include <stdio.h>

int compare_int(const void *a, const void *b)
{
    return *(int*)a - *(int*)b;
}

int main (void) {
    int x, n, p[100], i, j, c, flg = 0;

    scanf("%d %d", &x, &n);

    for (i = 0; i < n; i++) {
        scanf("%d", &(p[i]));
    }

    /*
     qsort(p, n, sizeof(int), compare_int);

    c = 0;

    for (i = 0; i < n; i++) {
        if (abs(x - p[i]) < abs(x - p[c])) {
            c = i;
        }
    }
    */

    for (i = 0; i < 200; i++) {
        flg = 0;
        c = (int)pow(-1, i) * (int)((i + 1) / 2);

        for (j = 0; j < 100; j++) {
            if (x + c == p[j]) {
                flg = 1;
                break;
            }
        }

        if (flg == 0) break;
    }

    printf("%d", x + c);

    return 0;
}