#include <bits/stdc++.h>   using namespace std;   const int siz = 1e5 + 7;   const int siz2 = 2e5 + 7;   int t, n;   int a[222];   int main() {     ios::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     cin >> t;   A:     while (t--) {       cin >> n;       map<int, int> mp;       vector<int> Ans;       for (int i = 0; i < n; ++i) {         cin >> a[i];         mp[a[i]]++;       }       if (n > 1) {         for (int i = 0; i < n; ++i) {           for (int j = a[i]; j <= 2 * n; ++j) {             if (!mp[j]) {               mp[j]++;               Ans.push_back(a[i]);               Ans.push_back(j);               break;             }           }         }         if (Ans.size() != 2 * n) {           cout << -1 << endl;           goto A;         }       } else {         if (a[0] == 1) {           cout << 1 <<     << 2 << endl;           goto A;         } else {           cout << -1 << endl;           goto A;         }       }       for (auto it : Ans) cout << it <<    ;       cout << endl;     }     return 0;   }   