Example

Input

5 3
4
2
5


Output

5
2
4
1
3
#include <bits/stdc++.h>

using namespace std;

#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define FOR(i, a, b) for(int i=(a);i<(b);i++)
#define REP(i, n) FOR(i, 0, n)
#define RFOR(i, a, b) for(int i=(a);i>=(b);i--)
#define RREP(i, n) RFOR(i, n, 0)
#define MFOR(i, m) for(auto i=(m).begin();i!=(m).end();i++)
#define ALL(a) (a).begin(), (a).end()
#define SZ(x) ((int)(x).size())

typedef long long int ll;
typedef pair<int, int> P;
typedef pair<ll, ll> Pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vll;
typedef vector<vll> vvll;

const double eps = 1e-10;
const int MOD = 1000000007;
const int INF = 1000000000;
const ll LINF = 1 << 30;

template<typename T>
void printv(vector<T> const& s) {
  REP(i, SZ(s)) {
    cout << s[i] << " ";
  }
  cout << endl;
}

int main () {
  cin.tie(0);
  cout << setprecision(10);

  int n, m; cin >> n >> m;
  vector<bool> sel(n+1, false);
  vi a;
  REP(i, m) {
    int tmp; cin>> tmp;
    a.pb(tmp);
  }
  reverse(ALL(a));
  REP(i, m) {
    if(!sel[a[i]]) cout << a[i] << endl;
    sel[a[i]] = true;
  }
  FOR(i, 1, n+1) {
    if(!sel[i]) cout << i << endl;
  }
}

