#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
mt19937 rnd(1);
int n;
ll b[1000005];
vector<ll>a[2];
vector<pair<ll,ll>>res;
void work(vector<ll>&v)
{
    ll x=v.back();v.pop_back();
    ll y=v.back();v.pop_back();
    res.emplace_back(x,y);
    a[x+y>>1&1].push_back(x+y>>1);
}
bool work()
{
    shuffle(b+1,b+n+1,rnd);
    a[0].clear(),a[1].clear(),res.clear();
    for(int i=1;i<=n;++i)a[b[i]&1].push_back(b[i]);
    while(a[0].size()>1||a[1].size()>1)
    {
        int p=rnd()&1;
        if(a[p].size()>1)work(a[p]);
        else work(a[p^1]);
    }
    if(!a[0].size()||!a[1].size())
    {
        for(auto i:res)printf("%lld %lld\n",i.first,i.second);
        return 1;
    }
    return 0;
}
void solve()
{
    scanf("%d",&n);
    for(int i=1;i<=n;++i)scanf("%lld",b+i);
    bool fl=0;
    for(int i=1;i<=300;++i)
        if(work()){fl=1;break;}
    if(!fl)puts("-1");
}
int main()
{
    int _;scanf("%d",&_);
    while(_--)solve();
}