Example

Input

5 3
4
2
5


Output

5
2
4
1
3
#include <bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define rep(i,n) repl(i,0,n)
#define each(itr,v) for(auto itr:v)
#define pb(s) push_back(s)
#define mp(a,b) make_pair(a,b)
#define all(x) (x).begin(),(x).end()
#define dbg(x) cout<<#x"="<<x<<endl
#define maxch(x,y) x=max(x,y)
#define minch(x,y) x=min(x,y)
#define uni(x) x.erase(unique(all(x)),x.end())
#define exist(x,y) (find(all(x),y)!=x.end())
#define bcnt(x) bitset<32>(x).count()

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;
typedef pair<P, int> PPI;
typedef pair<ll, ll> PL;
typedef pair<P, ll> PPL;

#define INF INT_MAX/3

#define MAX_N 1000

int n,m;
vector<int> e;
bool used[222222];
bool showed[222222];

int main(){
	cin.sync_with_stdio(false);
	cin>>n>>m;
	memset(used,0,sizeof(used));
	rep(i,m){
		int ee;
		cin>>ee;
		e.pb(ee);
		used[ee]=true;
	}
	reverse(all(e));
	rep(i,e.size()){
		if(showed[e[i]])continue;
		cout<<e[i]<<endl;
		used[e[i]]=true;
		showed[e[i]]=true;
	}
	repl(i,1,n+1){
		if(!used[i])cout<<i<<endl;
	}
	return 0;
}