#include<bits/stdc++.h>
#define int long long int
#define fast ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
using namespace std;

void solve(){

    int n, k;   cin >> n >> k;
    vector<int> v(k), mi;
    vector<bool>isPre(n+1, false);
    
    for(int i = 0; i < k; i++){
        cin >> v[i];
        isPre[v[i]] = true;
    }
    
    for(int i = 1; i <= n; i++){
        if(!isPre[i]) mi.push_back(i);
    }
    isPre.clear();
    
    int j = 0;
    vector<int> ans;
    int mx = INT_MIN;
    for(int i = 0; i < k; i++){
        for(int l = j; l < mi.size(); l++){
            if(v[i] < mi[l]){
                j = l;
                break;
            }
            ans.push_back(mi[l]), mx = max(mx, mi[l]);
        }
        ans.push_back(v[i]);
        mx = max(mx, v[i]);
    }
    
    for(int i = mx + 1; i <= n; i++){
        ans.push_back(i);
    }
    
    for(int i = 0; i < ans.size(); i++) cout << ans[i] << "\n";
    

}

signed main(){
    fast;
    int t = 1;
    //cin >> t;
    while(t--){solve();}
    return 0;
}