//Author: Kevin
#include<bits/stdc++.h>
//#pragma GCC optimize("O2")
using namespace std;
#define ll long long
#define ull unsigned ll
#define pb emplace_back
#define mp make_pair
#define ALL(x) (x).begin(),(x).end()
#define rALL(x) (x).rbegin(),(x).rend()
#define srt(x) sort(ALL(x))
#define rev(x) reverse(ALL(x))
#define rsrt(x) sort(rALL(x))
#define sz(x) (int)(x.size())
#define inf 0x3f3f3f3f
#define pii pair<int,int>
#define lb(v,x) (int)(lower_bound(ALL(v),x)-v.begin())
#define ub(v,x) (int)(upper_bound(ALL(v),x)-v.begin())
#define uni(v) v.resize(unique(ALL(v))-v.begin())
#define longer __int128_t
void die(string S){puts(S.c_str());exit(0);}
mt19937_64 rnd(20210448);
vector<pair<ll,ll>> op;
bool dfs(vector<ll> vec)
{
	if(sz(vec)==1) return true;
	for(int i=0;i<sz(vec);i++)
		for(int j=i+1;j<sz(vec);j++) if((vec[i]^vec[j]^1)&1)
		{
			op.pb(vec[i],vec[j]);
			vector<ll> vec2;
			for(int k=0;k<sz(vec);k++)
				if(i!=k&&j!=k)
					vec2.pb(vec[k]);
			vec2.pb(vec[i]+vec[j]>>1);
			if(dfs(vec2)) return true;
			op.pop_back();
		}
	return false;
}
void brute_force(vector<ll> vec)
{
	assert(dfs(vec));
}
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int t;
	cin>>t;
	while(t--)
	{
		op.clear();
		int n;
		cin>>n;
		vector<ll> vec;
		multiset<ll> ms[4];
		for(int i=0;i<n;i++)
		{
			ll x;
			cin>>x;
			vec.pb(x);
			ms[x&3].insert(x);
		}
		while(n-sz(op)>7)
		{
			if(sz(ms[0])&&sz(ms[2])) break;
			if(sz(ms[1])&&sz(ms[3])) break;
			int x=rnd()%4;
			if(sz(ms[0])<2&&sz(ms[1])<2&&sz(ms[2])<2&&sz(ms[3])<2) break;
			while(sz(ms[x])<2) x=rnd()%4;
			ll val=rnd()%(*ms[x].rbegin()+1);
			ll A=*ms[x].lower_bound(val);
			ms[x].erase(ms[x].lower_bound(A));
			val=rnd()%(*ms[x].rbegin()+1);
			ll B=*ms[x].lower_bound(val);
			ms[x].erase(ms[x].lower_bound(B));
			op.pb(A,B);
			ll C=A+B>>1;
			ms[C&3].insert(C);
		}
		if(n-sz(op)<=7)
		{
			vector<ll> vec;
			for(int i=0;i<4;i++)
				for(auto x:ms[i])
					vec.pb(x);
			brute_force(vec);
		}
		else if(sz(ms[0])&&sz(ms[2]))
		{
			vector<ll> vec;
			vec.pb(*ms[0].begin());
			vec.pb(*ms[2].begin());
			ms[0].erase(ms[0].begin());
			ms[2].erase(ms[2].begin());
			multiset<ll> ms2[2];
			for(int i=0;i<4;i++)
				for(auto x:ms[i])
					ms2[i&1].insert(x);
			while(sz(ms2[0])>1||sz(ms2[1])>1)
			{
				if(sz(ms2[0])>1)
				{
					ll A=*ms2[0].begin();
					ll B=*ms2[0].rbegin();
					ms2[0].erase(ms2[0].lower_bound(A));
					ms2[0].erase(ms2[0].lower_bound(B));
					ll C=A+B>>1;
					op.pb(A,B);
					ms2[C&1].insert(C);
				}
				else
				{
					ll A=*ms2[1].begin();
					ll B=*ms2[1].rbegin();
					ms2[1].erase(ms2[1].lower_bound(A));
					ms2[1].erase(ms2[1].lower_bound(B));
					ll C=A+B>>1;
					op.pb(A,B);
					ms2[C&1].insert(C);
				}
			}
			for(int i=0;i<2;i++)
				for(auto x:ms2[i])
					vec.pb(x);
			brute_force(vec);
		}
		else if(sz(ms[1])&&sz(ms[3]))
		{
			vector<ll> vec;
			vec.pb(*ms[1].begin());
			vec.pb(*ms[3].begin());
			ms[1].erase(ms[1].begin());
			ms[3].erase(ms[3].begin());
			multiset<ll> ms2[2];
			for(int i=0;i<4;i++)
				for(auto x:ms[i])
					ms2[i&1].insert(x);
			while(sz(ms2[0])>1||sz(ms2[1])>1)
			{
				if(sz(ms2[0])>1)
				{
					ll A=*ms2[0].begin();
					ll B=*ms2[0].rbegin();
					ms2[0].erase(ms2[0].lower_bound(A));
					ms2[0].erase(ms2[0].lower_bound(B));
					ll C=A+B>>1;
					op.pb(A,B);
					ms2[C&1].insert(C);
				}
				else
				{
					ll A=*ms2[1].begin();
					ll B=*ms2[1].rbegin();
					ms2[1].erase(ms2[1].lower_bound(A));
					ms2[1].erase(ms2[1].lower_bound(B));
					ll C=A+B>>1;
					op.pb(A,B);
					ms2[C&1].insert(C);
				}
			}
			for(int i=0;i<2;i++)
				for(auto x:ms2[i])
					vec.pb(x);
			brute_force(vec);
		}
		if(sz(op)!=n-1)
			cout<<-1<<'\n';
		else for(auto pr:op)
			cout<<pr.first<<" "<<pr.second<<'\n';
	}
	return 0;
}