// This Code was made by Chinese_zjc_.
#include <bits/stdc++.h>
int T, n;
std::vector<long long> a, b;
std::bitset<17> dp[9][16];
std::vector<long long> d[5];
std::vector<std::pair<long long, long long>> ans;
long long lowbit(long long x) { return x ? x & -x : LLONG_MAX; }
signed main()
{
    std::ios::sync_with_stdio(false);
    std::cin >> T;
    while (T--)
    {
        ans.clear();
        std::cin >> n;
        a.resize(n);
        for (int i = 0; i != n; ++i)
            std::cin >> a[i];
        for (int i = 0; i != 4; ++i)
            d[i].clear();
        for (int i = 0; i != n; ++i)
            d[a[i] & 3].push_back(a[i]);
        for (int i = 0; i != 4; ++i)
            if (!d[i].empty())
            {
                long long min = LLONG_MAX;
                for (int j = d[i].size(); --j;)
                    min = std::min(min, lowbit(d[i][j] ^ d[i][j - 1]));
                if (min != LLONG_MAX)
                    for (int j = d[i].size(); --j;)
                        if ((d[i][j] ^ d[i][j - 1]) & min)
                        {
                            std::swap(d[i][j - 1], d[i].back());
                            break;
                        }
            }
        while (d[0].size() >= 3 || d[1].size() >= 3 || d[2].size() >= 3 || d[3].size() >= 3)
            for (int i = 0; i != 4; ++i)
                while (d[i].size() >= 3)
                {
                    long long v = d[i].back();
                    d[i].pop_back();
                    ans.push_back({v, d[i].back()});
                    v += d[i].back();
                    d[i].pop_back();
                    d[v >> 1 & 3].push_back(v >> 1);
                }
        a.clear();
        for (int i = 0; i != 4; ++i)
        {
            for (auto j : d[i])
                a.push_back(j);
            d[i].clear();
        }
        b = a;
        n = b.size();
        for (int i = 0; i != n; ++i)
            b[i] &= 15;
        for (int i = 0; i <= n; ++i)
            for (int j = 0; j != 16; ++j)
                dp[i][j].reset();
        dp[0][0].set(0);
        for (int i = 0; i != n; ++i)
            for (int j = 0; j != 16; ++j)
                for (int k = 1; k != 16; k <<= 1)
                    dp[i + 1][(j + b[i] * k) & 15] |= dp[i][j] << k;
        if (dp[n][0].test(16))
        {
            int cv = 0, cw = 16;
            for (int i = n; i--;)
                for (int j = 0; 1 << j <= cw; ++j)
                    if (dp[i][(cv - (b[i] << j)) & 15][cw - (1 << j)])
                    {
                        d[j].push_back(a[i]);
                        cv = (cv - (b[i] << j)) & 15;
                        cw -= 1 << j;
                        break;
                    }
            for (int i = 0; i != 4; ++i)
            {
                std::partition(d[i].begin(), d[i].end(), [&](long long x)
                               { return x & 1; });
                for (std::vector<long long>::iterator j = d[i].begin(); j != d[i].end(); j += 2)
                    ans.push_back({j[0], j[1]}), d[i + 1].push_back((j[0] + j[1]) >> 1);
            }
            for (auto i : ans)
                std::cout << i.first << ' ' << i.second << '\n';
        }
        else
            std::cout << -1 << '\n';
    }
    return 0;
}