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)

// clang-format off
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
using G = vector<vector<ll>>;
#define G(i, j) i, vector<ll>(j)
#define Gv(i, j, k) i, vector<ll>(j, k)
#define rep(i,n) for(ll i=0, i##_len=(n); i<i##_len; ++i)
#define rep1(i,n) for(ll i=1, i##_len=(n); i<=i##_len; ++i)
#define rrep(i,n) for(ll i=n-1; i>=0; --i)
#define rrep1(i,n) for(ll i=n; i>0; --i)
#define all(x) (x).begin(),(x).end()
#define SORT(x) sort(all(x))
#define SORT_DESC(x) sort((x).rbegin(),(x).rend())
#define pb push_back
#define mp make_pair
#define coutl cout<<fixed<<setprecision(10)
#define ANS(ans) cout<<ans<<endl
#define END(ans) ANS(ans); return
const ll LINF = (1LL << 62) - 1;
const int INF = (1 << 30) - 1;
template<class T>inline bool chmax(T &a, const T &b){if (a<b){a=b;return 1;}return 0;}
template<class T>inline bool chmin(T &a, const T &b){if (b<a){a=b;return 1;}return 0;}
// clang-format on

void solve(long long X, long long N, std::vector<long long> p) {
  ll a, s = INF;
  rep(i, 102) {
    if (find(all(p), i) != p.end())
      continue;
    ll d = abs(X - i);
    if (d < s) {
      a = i;
      s = d;
    }
  }
  ANS(a);
}

// clang-format off
int main() {
  long long X;
  scanf("%lld",&X);
  long long N;
  scanf("%lld",&N);
  std::vector<long long> p(N);
  for(int i = 0 ; i < N ; i++){
    scanf("%lld",&p[i]);
  }
  solve(X, N, std::move(p));
  return 0;
}