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>
#include<stdlib.h>

int main(void){

    int x,n;

    scanf("%d %d",&x,&n);
    // printf("%d %d",x,n);
    if (n==0){
        printf("%d\n",x);
        return 0;
    }

    int p[n];
    int min=0;
    int ans=0;
    int flag=0;

    for (int i=0;i<n;i++){
        scanf("%d",&p[i]);
        if (x==p[i])
            flag=1;
    }

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

    for (int i=1;i<100;i++){
        int flag1=0;
        int flag2=0;
        for (int j=0;j<n;j++){
            if (x-i==p[j])
                flag1=1;
            else if (x+i==p[j])
                flag2=1;
        }
        // printf("i=%d flag1=%d flag2=%d\n",i,flag1,flag2);
        if ((flag1==0 && flag2==0) || (flag1==0 && flag2==1)){
            printf("%d\n",x-i);
            break;
        }else if (flag1==1 && flag2==0){
            printf("%d\n",x+i);
            break;
        }

    }
    
    return 0;
}