#ifdef DEBUG
#define _GLIBCXX_DEBUG
#endif
//#pragma GCC optimize("O3")
#include<bits/stdc++.h>

#define pb push_back
using namespace std;
typedef long long ll;
typedef long double ld;

vector<ll> a[4];
vector<pair<ll, ll> > ans;

void op(int i, int j) {
    i %= 4;
    j %= 4;
    if(a[i].empty()){
        return;
    }
    assert(!a[i].empty());
    ll x = a[i].back();
    a[i].pop_back();
    assert(!a[j].empty());
    ll y = a[j].back();
    a[j].pop_back();
    assert((x + y) % 2 == 0);
    ll z = (x + y) / 2;
    a[z % 4].push_back(z);
    ans.push_back({x, y});
}

void finish() {
    assert(
            (a[0].empty() && a[2].empty())
            ||
            (a[1].empty() && a[3].empty())
    );
    while (true) {
        bool found = 0;
        for (int i = 0; i < 4; i++) {
            if (a[i].size() <= 1)
                continue;
            found = 1;
            while (a[i].size() >= 2)
                op(i, i);
        }
        if (!found)
            break;
    }
    for (int i = 0; i < 4; i++)
        for (int j = 0; j < i; j++)
            if (!a[i].empty() && !a[j].empty())
                op(i, j);
    int cnt = 0;
    for (int i = 0; i < 4; i++)
        cnt += a[i].size();
    assert(cnt == 1);
    for (auto it: ans)
        cout << it.first << " " << it.second << "\n";
    return;
}

bool check(int i) {
    if (a[i].empty())
        return false;
    sort(a[i].begin(), a[i].end());
    if (a[i][0] == a[i].back())
        return false;
    for (int j = 3;; j++) {
        ll x = (1ll << j);
        int p = -1;
        for (int q = 0; q < a[i].size(); q++)
            if (a[i][q] % x != a[i][0] % x)
                p = q;
        if (p == -1)
            continue;
        if (j > a[i].size())
            return false;
        swap(a[i][p], a[i][a[i].size() - 1]);
        swap(a[i][0], a[i][a[i].size() - 2]);
        op(i, i);
        if (j > 3)
            check(i);
        return true;
    }
    assert(0);
}

mt19937 rnd(228);
void solve() {
    ans.clear();
    for (int i = 0; i < 4; i++)
        a[i].clear();
    {
//        int n = rnd() % 7 + 1;
//        while (n--) {
//            ll x = rand() % 100;
//            cout << x << " ";
//            a[x % 4].push_back(x);
//        }
//        cout << endl;
        int n;
        cin >> n;
        while (n--) {
            ll x;
            cin >> x;
            a[x % 4].pb(x);
        }
    }
    int cnt = 0;
    for (int i = 0; i < 4; i++)
        if (!a[i].empty())
            cnt++;
    if (a[0].empty() && a[2].empty()) {
        finish();
        return;
    }
    if (a[1].empty() && a[3].empty()) {
        finish();
        return;
    }
    if (cnt == 2) {
        bool found = 0;
        for (int i = 0; i < 4; i++)
            if (check(i)) {
                found = 1;
                break;
            }
        if (!found) {
            cout << "-1\n";
            return;
        }
        cnt++;
    }
    while (true) {
        bool found = 0;
        for (int i = 0; i < 4; i++) {
            if (a[i].size() <= 2)
                continue;
            found = 1;
            while (a[i].size() > 2)
                op(i, i);
        }
        if (!found)
            break;
    }
    if (cnt == 4) {
        for (int it = 0; it < 5; it++) {
            while (a[0].size() >= 2)
                op(0, 0);
            while (a[2].size() >= 2)
                op(2, 2);
            while (a[0].size() >= 1 && a[2].size() >= 1)
                op(0, 2);
        }
    }
    while (true) {
        bool found = 0;
        for (int i = 0; i < 4; i++) {
            if (a[i].size() <= 2)
                continue;
            found = 1;
            while (a[i].size() > 2)
                op(i, i);
        }
        if (!found)
            break;
    }
    if (a[0].empty() && a[2].empty()) {
        finish();
        return;
    }
    if (a[1].empty() && a[3].empty()) {
        finish();
        return;
    }
    int x = 0;
    if (a[x].empty() || a[x + 2].empty())
        x ^= 1;
    if (a[x].size() == a[x + 2].size()) {
        while (!a[x].empty())
            op(x, x + 2);
        finish();
        return;
    } else {
        for (int it = 0; it < 5; it++) {
            while (a[x ^ 1].size() >= 2)
                op(x ^ 1, x ^ 1);
            while (a[(x ^ 1) + 2].size() >= 2)
                op(x ^ 1 + 2, x ^ 1 + 2);
        }
        while (a[x ^ 1].size() >= 1 && a[(x ^ 1) + 2].size() >= 1)
            op(x ^ 1, (x ^ 1) + 2);
        if(a[x ^ 1].empty() && a[x ^ 1 + 2].empty()){
            finish();
            return;
        }
        if (a[x].size() == 1) {
            if (a[x + 2][0] % 8 == a[x + 2][1] % 8) {
                op(x + 2, x + 2);
                op(x, x + 2);
                finish();
                return;
            }
            int z = x ^ 1;
            if (a[z].empty())
                z += 2;
            if ((a[x][0] + a[x + 2][1]) / 2 % 4 == z)
                swap(a[x + 2][0], a[x + 2][1]);
            op(x, x + 2);
            op(z, z + 2);
            finish();
            return;
        } else {
            if (a[x][0] % 8 == a[x][1] % 8) {
                op(x, x);
                op(x, x + 2);
                finish();
                return;
            }
            int z = x ^ 1;
            if (a[z].empty())
                z += 2;
            if ((a[x][1] + a[x + 2][0]) / 2 % 4 == z)
                swap(a[x][0], a[x][1]);
            op(x, x + 2);
            op(z, z + 2);
            finish();
            return;
        }
    }
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
#ifdef DEBUG
    freopen("input.txt", "r", stdin);
#endif
    int t = 1;
    cin >> t;
    while (t--)
        solve();
    return 0;
}