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)

#include <bits/stdc++.h>
/*#include <boost/multiprecision/cpp_dec_float.hpp>
#include <boost/multiprecision/cpp_int.hpp>
*/#pragma GCC target("avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")    
using namespace std;
/*namespace mp = boost::multiprecision;
using Bint = mp::cpp_int;
using Real = mp::number<mp::cpp_dec_float<1024>>;
*/#define lli long long int
#define uli unsigned long long int
#define INF 999999999999
#define rep(i,m,n) for(lli i = m;i < n;i++)
#define rrep(i,m,n) for(lli i=m-1;i>=n;i--)
#define pb(n) push_back(n)
#define UE(N) N.erase(unique(N.begin(),N.end()),N.end());
#define Sort(n) sort(n.begin(), n.end())
#define Rev(n) reverse(n.begin(),n.end())
#define Out(S) cout << S << endl
#define NeOut(S) cout << S
#define HpOut(S) cout << setprecision(50) << S << endl
#define Vec(K,L,N,S) vector<L> K(N,S)
#define DV(K,L,N,M,S) vector<vector<L>> K(N,vector<L>(M,S))
#define TV(K,L,N,M,R,S) vector<vector<vector<L>>> K(N,vector<vector<L>>(M,vector<L>(R,S)))
#define pint pair<lli,lli>
#define paf(L,R) pair<L,R>
#define mod 998244353
#define MAX 10000000
#define ALL(a)  a.begin(),a.end()
#define chmax(a, b) a = (((a)<(b)) ? (b) : (a))
#define chmin(a, b) a = (((a)>(b)) ? (b) : (a))
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
int main(){
  ios::sync_with_stdio(false);
  cin.tie(0);
  lli A,B,C,D,E,H,W,M,K,L,R,N,num=0,sum=0,flag=0;string S,T;
  map<lli,lli>mp;
  map<string,lli>ms;
  cin >> N >> K;
  Vec(P,lli,110,0);
  rep(i,0,K){
      cin >> A;
      P[A]=1;
    }
    num=INF;
    rep(i,-200,200){
        if(i>-1){
            if(!P[i])chmin(num,abs(i-N));    
        }
        else chmin(num,abs(i-N));
    }
    sum=INF;
    if(N-num>=0){
        if(!P[N-num])sum=(N-num);
    }
    if(sum==INF&&!P[N+num])sum=(N+num);
    Out(sum);

}