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>

int main(void){

    int X, N,min=100, ans;
    int p[100], er[200], flag;
    scanf("%d %d", &X, &N);

    for(int j=1;j<200;j++){
        er[j]=0;
    }
    
    if(N==0){
        printf("%d",X);
    }
    else{
        for(int i=0;i<N;i++){
            scanf("%d", &p[i]);
            ans = X-p[i];
            if(ans>0){
                er[2*ans-1]=1;
            }
            else if(ans<0){
                er[2*ans]=1;
            }
            else{
                er[0]=1;
            }
        }

        for(int k=0;k<200;k++){
            if(er[k]!=0){
                if(k%2==1){
                    printf("%d", X-(int)((k+1)/2));
                    break;
                }
                else if(k%2==0){
                    printf("%d", X+(int)((k+1)/2));
                }
            }
        }

        
    }
    return 0;
}