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 <string.h>
#include <stdlib.h>

int x, n, p[100];
int resolvel(int a)
{
  if ( a<1 )
    return 999; // not found
  if ( !p[a-1] )
    return a;
  return resolvel(a-1);
}
int resolveh(int a)
{
  if ( a>100 )
    return 999; // not found
  if ( !p[a-1] )
    return a;
  return resolveh(a+1);
}
int main()
{
  scanf("%d %d", &x, &n);
  for ( int i=0; i<n; i++ ) {
    int num;
    scanf("%d", &num);
    p[num-1] = 1;
  }
  int l, h;
  l = resolvel(x);
  h = resolveh(x);
  printf("%d\n", abs(x-l)<abs(x-h)? l: h);

  return 0;
}