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>

int main(void)
{	int X, N;
	int num[102] = {0};
	int i, tmp, sub, ans;

	scanf("%d %d", &X, &N);

	if (N == 0)
	{
		printf("%d\n", X);
		return (0);
	}

	for (i = 0; i < N; i++)
	{
		scanf("%d", &tmp);
		num[tmp]++;
	}

	i = 101;
	sub = 102;
	while (0 <= i)
	{
		if (0 < num[i])
		{
			i--;
			continue;
		}
		tmp = X - i;
		if (tmp < 0)
			tmp *= -1;
		if (tmp <= sub)
			ans = i;
		else
			break;
		sub = X - i;
		if (sub < 0)
			sub *= -1;
		i--;
	}
	printf("%d\n", ans);

	return (0);
}