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<stdlib.h>
int asc(const void *a, const void *b) {
  return *(int *)a - *(int *)b;
}

int main(){
  int x,y,n[100]={};
  int i,ans,xm,xu,xf=0;
  scanf("%d %d",&x,&y);
  ans=x;
  xm=x-1;
  xu=x+1;
  if(y!=0){
    for(i=0;i<y;i++)scanf("%d",&n[i]);
    qsort(n,100,sizeof(int),asc);
    for(i=99;i>=100-y;i--){
      if(xm==n[i])
        xm--;
      if(xu==n[i])
        xu++;
      if(x==n[i])
        xf=1;
    }
    if(xf==0)
      ans=x;
    else if(x-xm<=xu-x)
      ans=xm;
    else 
      ans=xu;
  }
  printf("%d",ans);
  return 0;
}