#include <iostream>
#include <bits/stdc++.h>

using namespace std;

#define ll                  long long int
#define ii                  pair<int,int>
#define pb                  push_back
#define all(a)              (a).begin(), (a).end()
#define FOR(i, l, r)        for(int i = l; i < r ; i ++)
#define seeList(A)          if(debug) { bool leonelCheems = 0; cerr << "[ ";  for(auto x : A) { if(!leonelCheems) cerr << x , leonelCheems = 1; else cerr << " , " << x ;} cerr << " ]" << endl; }
#define seeVar(A)           if(debug) { cerr << "{ " << A << " }" << endl; }
#define executeTime         cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";

const int    N       =      2e5  + 9;
const int    mod     =      1e9  + 7;
const int    inf     =      2e9  + 9;
const ll     modL    =      1e9  + 7;
const ll     infL    =      2e18 + 9;
const double pi      =      acos(-1);

// si no vas por todo, anda pa ashá bobo
// mirame a la cara, lo siento pero te como hermano * bailecito *

bool debug = { 1 };
bitset<N> marked;

void cumbia420PaLosNegros(int testCase) { /* aguante la falopa wacho y la gente de la cashe :v */
    int n, k; cin >> n >> k;
    queue<int> A, B;

    FOR(i, 0, k) {
        int x; cin >> x;
        marked[x] = 1;
        A.push(x);
    }

    FOR(i, 1, n + 1) {
		if(!marked[i]) B.push(i);
	}

    //seeList(S);
	int it = 0;
    while(A.size() || B.size()) {
		it ++;
        if(A.empty()) {
			while(!B.empty()) {
				cout << B.front() << endl;
				B.pop();
			}
			return;
        }
        else if(B.empty()) {
            while(!A.empty()) {
				cout << A.front() << endl;
				A.pop();
			}
			return;
        }
        else {
            if(A.front() < B.front()) {
                cout << A.front() << endl;  A.pop();
            }
            else {
                cout << B.front() << endl; 	B.pop();
            }
        }
    }
	assert(it <= n + 1);
}

int main() {
	cin.tie(0); ios_base::sync_with_stdio(0);
	cerr << "! ready " << endl;
	int t = 1;
	//cin >> t;
	FOR(i, 1, t + 1) cumbia420PaLosNegros(i);
	executeTime
	return 0;
}