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 <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
const ll MOD = 1000000007;
const ld PI = acos(-1);  
const ld EPS = 0.0000000001;
const ll LINF = 1001002003004005006ll;
const int INF = 1001001001;
#define REP(i, n) for(ll i=0; i<(ll)(n); i++)
#define REPD(i, n) for(ll i=n-1; 0<=i; i--)
#define FOR(i, a, b) for(ll i=a; i<(ll)(b); i++)
#define FORD(i, a, b) for(ll i=a; (ll)(b)<=i; i--)
#define ALL(x) x.begin(), x.end()
#define MAX(x) *max_element(ALL(x))
#define MIN(x) *min_element(ALL(x))
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

int main(){
    ll x, n;    cin >> x >> n;
 
    map<ll, ll> key;
    REP(i, n){
        ll p;   cin >> p;
        key[p] += 1;
    }
    ll res=0;
    FOR(i, -101, 101){
        if(key.count(i)) continue;
        if(abs(i-x)<abs(res-x)) res = i;
    }
    cout << res << endl;
}