#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> P;
typedef vector<ll> vi;
typedef vector<vi> vvi;
typedef vector<P> vp;
typedef vector<vp> vvp;
#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
#define REP(i,k,n) for(ll i=(ll)(k);i<(ll)(n);i++)
#define all(a) a.begin(),a.end()
#define pb emplace_back
#define fi first
#define se second
template<class T> bool chmin(T&a,T b){if(a>b){a=b;return true;}return false;}
template<class T> bool chmax(T&a,T b){if(a<b){a=b;return true;}return false;}
template<class T> void out(T a){cout<<a<<'\n';}
template<class T> void outv(T v){rep(i,v.size()){if(i)cout<<' ';cout<<v[i];}cout<<'\n';}
template<class T> void outvv(T v){for(auto x:v)outv(x);}
const ll inf=1001001001001001001;
ll ord(ll a){
    if(a==0)return inf;
    ll ans=0;
    while(!(a&1)){
        a>>=1;ans++;
    }
    return ans;
}
vp ans;
vvi g;
ll d(ll a,ll b){
    assert(a%2==b%2);
    ans.pb(a,b);
    return (a+b)/2;
}
vi f(vi v){
    sort(all(v));
    ll n=v.size();
    P mi(inf,0);
    rep(i,n-1)chmin(mi,P(ord(v[i+1]-v[i]),i));
    ll cnt=mi.fi,cur=mi.se+1;
    while(cnt>1&&cur<n){
        v[mi.se]=d(v[mi.se],v[cur]);cnt--;cur++;
    }
    vi nv;
    rep(i,mi.se+1)nv.pb(v[i]);
    REP(i,cur,n)nv.pb(v[i]);
    while(cnt>1&&nv.size()>1){
        ll a=d(nv.back(),nv[nv.size()-2]);
        nv.pop_back();
        nv.back()=a;
        cnt--;
    }
    if(nv.size()==1)return nv;
    ll idx=0;
    while(ord(nv[idx+1]-nv[idx])>1)idx++;
    vi al;
    {
        ll cur=0;
        while(cur+1<idx){
            nv[cur+1]=d(nv[cur],nv[cur+1]);
            if(nv[cur+1]%2!=nv[cur]%2){
                g[nv[cur+1]%2].pb(nv[cur+1]);cur++;
            }
            cur++;
        }
        if(cur<idx)al.pb(nv[cur]);
    }
    al.pb(nv[idx]);al.pb(nv[idx+1]);
    {
        ll cur=nv.size()-1;
        while(cur-1>idx+1){
            nv[cur-1]=d(nv[cur],nv[cur-1]);
            if(nv[cur-1]%2!=nv[cur]%2){
                g[nv[cur-1]%2].pb(nv[cur-1]);cur--;
            }
            cur--;
        }
        if(cur>idx+1)al.pb(nv[cur]);
    }
    return al;
}
vi consume_all(vi v){
    while(v.size()>2){
        ll a=v[v.size()-3],b=v[v.size()-2],c=v.back();
        rep(j,3)v.pop_back();
        if((a+b)/2%2==a%2){
            v.pb(c);v.pb(d(a,b));
        }
        else if((b+c)/2%2==b%2){
            v.pb(a);v.pb(d(b,c));
        }
        else{
            v.pb(b);v.pb(d(c,a));
        }
    }
    if(v.size()==2){
        v[0]=d(v[0],v[1]);v.pop_back();
    }
    return v;
}
void solve(ll n,vi v){
    ans=vp(0);g=vvi(2);
    for(ll x:v)g[x%2].pb(x);
    if(g[0].size()==0){
        consume_all(g[1]);
        return;
    }
    if(g[1].size()==0){
        consume_all(g[0]);
        return;
    }
    g[0]=f(g[0]);
    ll swapped=0;
    if(g[0].size()==1){
        g[1]=f(g[1]);
    }
    else{
        swapped=1;
        swap(g[0],g[1]);
    }
    if(g[0].size()==1&&g[1].size()==1)return;
    g[0]=consume_all(g[0]);
    if(g[0][0]%2!=swapped){
        g[1].pb(g[0][0]);
        consume_all(g[1]);
        return;
    }
    if(g[1].size()==2){
        g[0].pb(d(g[1][0],g[1][1]));
        consume_all(g[0]);
        return;
    }
    rep(i,g[1].size())rep(j,i){
        ll t=(g[1][i]+g[1][j])/2,u=g[0][0];
        if(t%4!=u%4&&t%2==u%2){
            vi ng;
            ng.pb(d(d(g[1][i],g[1][j]),u));
            rep(k,g[1].size())if(i!=k&&j!=k)ng.pb(g[1][k]);
            consume_all(ng);
            return;
        }
    }
}
int main(){
    cin.tie(0);ios::sync_with_stdio(false);
    ll t;cin>>t;
    rep(tt,t){
        ll n;cin>>n;
        vi v(n);rep(i,n)cin>>v[i];
        solve(n,v);
        if(ans.size()==n-1){
            for(auto x:ans)cout<<x.fi<<' '<<x.se<<endl;
        }
        else{
            out(-1);
        }
    }
}