#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int MAXN = 1e6 + 5;

int n;
ll a[MAXN];

namespace Subtask1
{
	vector< pair<ll,ll> > seq;
	bool del[10];
	bool valid;
	
	void dfs(int dep)
	{
		if(valid) return;
		if(dep == n-1)
		{
			for(auto t: seq)
				printf("%lld %lld\n",t.first,t.second);
			valid = 1;
			return;
		}
		for(int i=1; i<=n; ++i) if(!del[i])
			for(int j=1; j<i; ++j) if(!del[j] && (a[i] & 1) == (a[j] & 1))
			{
				ll x = a[i], y = a[j];
				del[j] = 1; a[i] = (x + y) >> 1;
				seq.emplace_back(x, y);
				
				dfs(dep + 1);
				
				if(valid) return;
				
				del[j] = 0; a[i] = x; a[j] = y;
				seq.pop_back();
			}
	}
	
	void solve(void)
	{
		seq.clear();
		memset(del, 0, sizeof(del));
		valid = 0;
		dfs(0);
		if(!valid)
			printf("-1\n");
	}
}

namespace Subtask2
{
	int cnt[11];
	vector<pii> seq;
	
	bool valid;
	
	void dfs(int dep)
	{
		if(valid) return;
		if(dep == n-1)
		{
			for(auto t: seq)
				printf("%d %d\n",t.first,t.second);
			valid = 1;
			return;
		}
		for(int i=1; i<=10; ++i) if(cnt[i])
			for(int j=i&1; j<=i; j+=2) if(cnt[j])
			{
				int k = (i + j) >> 1;
				--cnt[i]; --cnt[j]; ++cnt[k];
				seq.emplace_back(i, j);
				
				dfs(dep + 1);
				
				if(valid) return;
				
				++cnt[i]; ++cnt[j]; --cnt[k];
				seq.pop_back();
			}
	}
	
	void solve(void)
	{
		memset(cnt, 0, sizeof(cnt));
		for(int i=1; i<=n; ++i)
			++cnt[a[i]];
		
		dfs(0);
		
		if(!valid) printf("-1\n");
	}
}

void solve(void)
{
	scanf("%d",&n);
	for(int i=1; i<=n; ++i)
		scanf("%lld",&a[i]);
	
	vector<ll> vec[4];
	for(int i=1; i<=n; ++i)
		vec[a[i] % 4].emplace_back(a[i]);
	
	if(vec[1].size() || vec[3].size())
	{
		if(n <= 7)
			Subtask1 :: solve();
		else
			Subtask2 :: solve();
		return;
	}
	
	auto upd = [&] (int i,int j)
	{
		ll x = vec[i].back(); vec[i].pop_back();
		ll y = vec[j].back(); vec[j].pop_back();
		
		printf("%lld %lld\n",x,y);
		
		ll z = (x + y) / 2;
		vec[z % 4].emplace_back(z);
	};
	while(vec[0].size() >= 2 || vec[2].size() >= 2)
	{
		if(vec[0].size() >= 2) upd(0, 0);
		if(vec[2].size() >= 2) upd(2, 2);
	}
	while(vec[0].size() && vec[2].size()) upd(0, 2);
}

int main(void)
{
	int T;
	scanf("%d",&T);
	while(T--) solve();
	return 0;
}