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<cstdio>
#include<algorithm>
#include<functional>
using namespace std;
int main(void)
{
	int x,n,p,flg[101],i,mn,mi,sa;
	scanf("%d %d",&x,&n);
	for(i=1;i<=100;i++)	flg[i]=0;
	for(i=0;i<n;i++)	{
		scanf("%d",&p);
		flg[p]=1;
	}
	mn=100;
	for(i=1;i<=100;i++)	{
		if(flg[i]==0)	{
			sa=i-x;
			if(sa<0)	sa=-sa;
			if(sa<mn)	{
				mn=sa;
				mi=i;
			}
		}
	}
	printf("%d\n",mi);
	return 0;
}