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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#define ll long long
#define ull unsigned long long

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

int main(){
    int i,x,n,p[102]={},num=1;
    scanf("%d%d",&x,&n);
    for (i=0; i<n; i++) scanf("%d",&p[i]);
    qsort(p, n, sizeof(p[0]), compare_smallorder);
    for (i=0; i<n; i++) {
        if (p[i]==x) break;
    }
    if (i==n) {
        printf("%d",x);
        return 0;
    }
    while (1) {
        for (i=0; i<n; i++) {
            if (p[i]==x-num) break;
        }
        if (i==n) {
            printf("%d",x-num);
            return 0;
        }
        for (i=0; i<n; i++) {
            if (p[i]==x+num) break;
        }
        if (i==n) {
            printf("%d",x+num);
            return 0;
        }
        num++;
    }
    return 0;
}