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 <math.h>

int main(void)
{
  int i, n, x, p[100], q[101] = {0}, result = 200, num = 200;
  
  scanf("%d %d", &x, &n);
  
  
  
  for( i = 0; i < n; i++ ){
      scanf("%d", &p[i]);
      q[p[i]] = 1;
  }
  
  for( i = 0; i < 102; i++ ){
    if( q[i] == 0 ){
        if( i <= x ){
            if( result > x - i ){
                result = x - i;
                num = i;
            }
        }
        if( i > x ){
            if( result > i - x ){
                result = i - x;
                num = i;
            }
        }
    }
  }
  
  if( num == 200 ){
      printf("-1\n");
  } else {
  printf("%d\n", num);
  }
  return 0;
}