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++ (Clang 10.0.0) (judge verdict: Wrong Answer)

#include<iostream>
#include<algorithm>

using namespace std;

int a[1000]={0};

int main(){
	int x,n;
	cin>>x>>n;
	if(n==0) cout<<x<<endl;
	else{
	int re;
	for(int i=0;i<n;i++){
	cin>>re;
	a[re]++;	
	}
	int ans,res,ans1,res1;
	for(int i=x;i<=100;i++){
		if(a[i]==0){
		ans = i - x;
		res = i;
		break;	
		} 
	}
	for(int i=1;i<x;i++){
		if(a[i]==0){
		ans1 = x - i;
		res1 = i;	
		}
	}
	//cout<<ans<<" "<<res<<endl;
	//cout<<ans1<<" "<<res1<<endl;
	if(ans <ans1) cout<<res<<endl;
	else if(ans = ans1) cout<<min(res,res1)<<endl;
	else cout<<res1<<endl;
	}
	return 0;
}