#include <cstdio>
#include <cstring>
#include <cmath>
#include <cctype>
#include <iostream>
#include <algorithm>
#include <map>
#include <set>
#include <vector>
#include <string>
#include <stack>
#include <queue>
 
typedef long long LL;
using namespace std;
 
int n, m;
int a[100005], vis[100005];
 
int main()
{
	//freopen("in.txt", "r", stdin);
	//freopen("out.txt", "w", stdout);
 
	scanf("%d %d", &n, &m);
	for (int i = 1; i <= m; i++){
		scanf("%d", &a[i]);
	}
	for (int i = m; i >= 1; i--){
		if(vis[a[i]]) continue;
		vis[a[i]] = 1;
		printf("%d ", a[i]);
	}
	for (int i = 1; i <= n; i++){
		if(!vis[i]) printf("%d ", i);
	}
	printf("\n");
 
	return 0;
}