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>
int cmp(const void *a, const void *b){return *(int*)a - *(int*)b;}
int min(int a, int b){return a < b ? a : b;}
int main(){
    int x, n;
    scanf("%d%d",&x,&n);
    if(n == 0){
        printf("%d\n",x);
        return 0;
    }
    int p[n];
    for(int i = 0;  i < n; i++)
        scanf("%d",&p[i]);
    int q[101];
    for(int i = 0; i <= 100; i++)
        q[i] = 0;
    qsort(p,n,4,cmp);
    for(int i = 0; i < n; i++)
        q[p[i]] = 1;
    int di = 11110;
    int ans = 0;
    for(int i = 1; i <= 100; i++){
        if(q[i])
            continue;
        int d = abs(i - x);
        if(d < di){
            di = d;
            ans = i;
        }
    }
    if(ans > p[n - 1] && ans > x)
        ans = 0;
    printf("%d\n",ans);
    return 0;
}