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)


// Problem : C - Forbidden List
// Contest : AtCoder - AtCoder Beginner Contest 170
// URL : https://atcoder.jp/contests/abc170/tasks/abc170_c?lang=en
// Memory Limit : 1024 MB
// Time Limit : 2000 ms
// Powered by CP Editor (https://github.com/cpeditor/cpeditor)

#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=1;i<=(int)n;i++)
#define REP(i,n) for(int i=0;i<(int)n;i++)
#define ll long long
#define mod 1000000007
const ll INF = 1000000001;
int lcm(int x,int y){
	return x/__gcd(x,y)*y;
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n,m;
    cin>>n>>m;
    set<int>st;
    for(int i=0;i<m;i++){
    	int x;
    	cin>>x;
    	st.insert(x);
    }
    int ans=INF;
    int diff=INF;
    for(int i=1;i<=100;i++){
    	if(st.count(i))continue;
    	int di=abs(n-i);
    	if(di<diff){
    		diff=di;
    		ans=i;
    	}
    }
    cout<<ans<<endl;
    return 0;
}