#include<bits/stdc++.h>
using namespace std;
int main()
{
	int a[100010],f[100010]={0};
	int n,m,i,j;
	cin>>n>>m;
	for(i=0;i<m;i++){
		cin>>a[i];
	}
	for(i=m-1;i>=0;i--){
		if(f[a[i]]==0){
			cout<<a[i]<<" ";
			f[a[i]]=1; 
		} 
	}
	for(i=1;i<=n;i++){
		if(f[i]==0){
			cout<<i<<" ";
		}
	}
    return 0;
}


/**************************************************************
	Problem: 1527
	User: zhuangsongyu
	Language: C++
	Result: Accepted
	Time:157 ms
	Memory:2732 kb
****************************************************************/