#include <iostream>
using namespace std;

const int MAX = 1e5+5;
bool f[MAX];
int a[MAX], m, n;

int main()
{
    cin >> n >> m;
    for (int i=1; i<=m; i++) cin >> a[i];


    for (int i=m; i>=1; i--)
    {
        if (!f[a[i]])
        {
            f[a[i]]=true;
            cout<<a[i]<<" ";
        }
    }
    for (int i=1; i<=n; i++)
    {
        if (!f[i]) cout<<i<<" ";
    }
    return 0;
}