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 X,N,i,j,tmp;
  scanf("%d %d",&X,&N);
  if(N==0){
    printf("%d",X);
    return 0;
  }
  int p[N];
  for(i=0; i<N; i++){
    scanf("%d",&p[i]);
    p[i] = p[i] - X;
  }
  for (i=0; i<N; i++) {
    for (j=i+1; j<N; j++) {
      if (abs(p[i]) > abs(p[j])) {
        tmp =  p[i];
        p[i] = p[j];
        p[j] = tmp;
      }
    }
  }
  int flag;
 
  for(i=0; i<102; i++){
    flag = 1;
    for(j=0; j<N; j++){
      if(abs(p[j]) == i){
	if(i == 0) flag = 0;
	else{
	  if(j==N-1){
	    flag = 0;
	  }
	  else{
	    if(abs(p[j+1]) == i){
	      flag = 0;
	      j++;
	    }
	    else{
	      if(p[j] == i*(-1)){
		flag = 2;
	      }
	    }
	  }
	}
      }
    }
    if(flag == 1){
      printf("%d",i*(-1)+X);
      return 0;
    }
    if(flag == 2){
      printf("%d",i+X);
      return 0;
    }
  }
}