#include <bits/stdc++.h>

using namespace std;

const int N = 1e6 + 5;

int n;
long long a[N];
vector<long long> p[2];
mt19937 rnd;

int check() {
    p[0].clear(), p[1].clear();
    for (int i = 1; i <= n; ++i) {
        p[a[i] & 1].push_back(a[i]);
    }
    vector< pair<int, int> > tp;
    for (int i = 1; i < n; ++i) {
        if (p[0].size() < 2 && p[1].size() < 2) return 0;
        int t = rnd() & 1;
        if (p[t].size() >= 2) {
            tp.push_back({p[t].end()[-2], p[t].back()});
            long long v = (p[t].end()[-2] + p[t].back()) >> 1;
            p[t].pop_back(), p[t].pop_back(), p[v & 1].push_back(v);
            continue;
        }
        t ^= 1;
        if (p[t].size() >= 2) {
            tp.push_back({p[t].end()[-2], p[t].back()});
            long long v = (p[t].end()[-2] + p[t].back()) >> 1;
            p[t].pop_back(), p[t].pop_back(), p[v & 1].push_back(v);
        }
    }
    for (auto [x, y] : tp) printf("%d %d\n", x, y);
    return 1;
}

signed main() {
    int T; scanf("%d", &T);
    while (T--) {
        scanf("%d", &n);
        for (int i = 1; i <= n; ++i) scanf("%lld", &a[i]);
        int flg = 0;
        for (int i = 0; i < 100; ++i) {
            shuffle(a + 1, a + n + 1, rnd);
            if (check()) {
                flg = 1;
                break;
            }
        }
        if (!flg) puts("-1");
    }
    return 0;
}