#include<bits/stdc++.h>
using namespace std;
int main(){
	int a[100080],f[900000]={0},n,m,x,i,j,t;
	cin>>n>>m;
	for(int i=0;i<m;i++){
		cin>>a[i];
	}
	for(int i=m-1;i>=0;i--){
		if(f[a[i]]==0){
			cout<<a[i]<<" ";
			f[a[i]]=1;
		}
	}
	for(int i=1;i<=n;i++){
		if(f[i]==0){
			cout<<i<<" ";
		}
	}
} 
/**************************************************************
	Problem: 1527
	User: zhengzihao
	Language: C++
	Result: Accepted
	Time:223 ms
	Memory:5860 kb
****************************************************************/