#include <bits/stdc++.h>

using namespace std;
using ll = long long;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int test = 1;
    cin >> test;

    while (test--) {
        int n;
        cin >> n;

        vector<ll> a(n);

        for (int i = 0; i < n; ++i) {
            cin >> a[i];
        }

        stable_partition(a.begin(), a.end(), [&](ll x) { return x % 2 == 0; });

        if (a[n - 1] % 2 == 1 && a[n - 2] % 2 == 0) {
            cout << "-1\n";
            continue;
        }
        
        while (size(a) > 1) {
            cout << a.back() << " " << a.end()[-2] << '\n';
            a.end()[-2] += a.back();
            a.pop_back();
        }
    }

    return 0;
}