#include <bits/stdc++.h>
using namespace std;
#define debug(fmt, ...) \
  fprintf(stderr, "[%d] " fmt "\n", __LINE__, ##__VA_ARGS__)
template <class _Tx, class _Ty>
inline void chkmin(_Tx& x, const _Ty& y) { if (y < x) x = y; }
template <class _Tx, class _Ty>
inline void chkmax(_Tx& x, const _Ty& y) { if (x < y) x = y; }
bool Mbe;
using ll = long long;
constexpr int N = 1e6 + 10;
int n;
ll a[N];
mt19937 rng{19260817};
void mian() {
  cin >> n;
  for (int i = 1; i <= n; ++i) cin >> a[i];
  for (int tt = 0; tt < 400; ++tt) {
    vector<ll> vec[2];
    vector<pair<ll, ll>> out;
    for (int i = 1; i <= n; ++i) vec[a[i] & 1].push_back(a[i]);
    shuffle(vec[0].begin(), vec[0].end(), rng);
    shuffle(vec[1].begin(), vec[1].end(), rng);
    while (vec[0].size() > 1 || vec[1].size() > 1) {
      ll x, y, z;
      int p = [&]() -> int {
        if (vec[0].size() <= 1) return 1;
        if (vec[1].size() <= 1) return 0;
        return rng() & 1;
      }();
      x = vec[p].back(), vec[p].pop_back();
      y = vec[p].back(), vec[p].pop_back();
      z = (x + y) >> 1, vec[z & 1].push_back(z);
      out.push_back({x, y});
    }
    if (vec[0].empty() || vec[1].empty()) {
      for (auto it : out) cout << it.first << ' ' << it.second << '\n';
      return;
    }
  }
  cout << "-1\n";
}
bool Med;
int main() {
  // debug("Mem: %.4lfMB.", fabs(&Med - &Mbe) / 1048576);
  cin.tie(0)->sync_with_stdio(0);
  int cas;
  cin >> cas;
  while (cas--) mian();
  return 0;
}
/*
g++ -std=c++14 -O2 -o D D.cpp -Wall -Wextra
-Wshadow -fsanitize=address,undefined -g
*/