#include <bits/stdc++.h>

using namespace std;

namespace {

#define VEVE(i, a, b) for (ll i = a, __##i = b; i < __##i; ++i)
#define RARA(i, a, b) for (ll i = a, __##i = b; i > __##i; --i)
#define VERA(x, seq) for (auto &x : seq)
#define SIZE(x) ((ll)(x.size()))
#define ALL(x) x.begin(), x.end()

typedef int ll;
typedef double dd;

void Solve(ll) {
  ll n, m;
  cin >> n >> m;
  set<ll> rem;
  VEVE(i, 1, n + 1) rem.insert(i);
  vector<ll> seq(m);
  VERA(s, seq) {
    cin >> s;
    rem.erase(s);
  }
  vector<ll> oth(ALL(rem));
  vector<ll> res;
  merge(ALL(seq), ALL(oth), back_inserter(res));
  VERA(r, res) cout << r << '\n';
}

void Init() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
}
}

int main() {
#ifdef AZN
  freopen("input.txt", "r", stdin);
#endif
  Init();
  ll tests = 1;
  VEVE(test, 1, tests + 1) Solve(test);
  return 0;
}