//A tree without skin will surely die.
//A man without face will be alive.
#include<bits/stdc++.h>
using namespace std;
#define all(x) (x).begin(),(x).end()
#define rep(i,j,k) for (int i=j;i<=k;++i)
#define per(i,j,k) for (int i=j;i>=k;--i)
int const N=1e6+10;
mt19937 rnd(time(0));
int n,a[N];vector<int>c[2];
inline int work(){
    vector< pair<int,int> >ans;
    c[0].clear(),c[1].clear();
    shuffle(a+1,a+n+1,rnd);
    rep(i,1,n) c[a[i]&1].push_back(a[i]);
    rep(i,1,n-1){
        if (c[0].size()==1 && c[1].size()==1) return 0;
        vector<int>prio;
        prio.push_back(0),prio.push_back(1);
        shuffle(all(prio),rnd);
        for (auto it:prio)
            if (c[it].size()>1){
                int x=c[it].back();c[it].pop_back();
                int y=c[it].back();c[it].pop_back();
                ans.push_back({x,y});
                c[((x+y)/2)&1].push_back((x+y)/2);
                break;
            }
    }
    for (auto i:ans) cout<<i.first<<' '<<i.second<<'\n';
    return 1;
}
inline void solve(){
    cin>>n;
    rep(i,1,n) cin>>a[i];
    rep(T,1,400) if (work()) return;
    cout<<"-1\n";
}
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0),cout.tie(0);
    int t=1;
    cin>>t;
    while (t--) solve();
    cerr<<"Time: "<<(double)clock()/CLOCKS_PER_SEC<<" s\n";
    return 0;
}