#include <bits/stdc++.h>
using namespace std;
const int MAX = 200005;
int a[MAX];
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    bool flag = false;
    int maxc = n * 2;
    bool b[205];
    memset(b, false, sizeof(b));
    for (int i = 0; i < n; i++) {
      cin >> a[i];
      b[a[i]] = true;
      if (a[i] == maxc) {
        flag = true;
      }
    }
    if (flag) {
      cout << -1 << endl;
      continue;
    }
    vector<int> ans;
    for (int i = 0; i < n; i++) {
      for (int j = 1; j <= 2 * n; j++) {
        if (b[j] == false) {
          if (a[i] < j) {
            b[j] = true;
            ans.push_back(a[i]);
            ans.push_back(j);
            break;
          }
        }
      }
    }
    if (ans.size() != 2 * n) {
      cout << -1 << endl;
    } else {
      for (auto &q : ans) {
        cout << q << " ";
      }
      cout << endl;
    }
  }
  return 0;
}
