#include <bits/stdc++.h>
using namespace std;
int n, b[105];
void solve() {
  vector<int> a;
  vector<int> us(205, 0);
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> b[i];
    us[b[i]] = 1;
  }
  for (int i = 0; i < n; i++) {
    a.push_back(b[i]);
    int flag = 0;
    for (int j = 1; j <= 2 * n; j++) {
      if (us[j] == 0 && j > b[i]) {
        flag = 1;
        a.push_back(j);
        us[j] = 1;
        break;
      }
    }
    if (flag == 0) {
      cout << -1;
      return;
    }
  }
  for (int i = 0; i < a.size(); i++) {
    cout << a[i] << " ";
  }
}
int main() {
  int t = 1;
  cin >> t;
  while (t--) {
    solve();
    cout << endl;
  }
}
