//#include <bits/stdc++.h>
#include <iostream>
#include <iomanip>
#include <math.h>
#include <cmath>
#include <algorithm>
#include <climits>
#include <functional>
#include <cstring>
#include <string>
#include <cstdlib>
#include <ctime>
#include <cstdio>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <bitset>
#include <complex>
#include <random>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
#define itn int
#define nit int
#define ll long long
#define ms multiset
#define F(i,a,b) for(register int i=a,i##end=b;i<=i##end;++i)
#define UF(i,a,b) for(register int i=a,i##end=b;i>=i##end;--i)
#define re register
#define ri re int
#define il inline
#define pii pair<ll,ll>
#define cp complex<double>
#define vi vector<int>
#define ull unsigned long long
#define mem0(x) memset(x,0,sizeof(x))
#define mem0x3f(x) memset(x,0x3f,sizeof(x))
using namespace std;
using std::bitset;
//using namespace __gnu_pbds;
const double Pi=acos(-1);
namespace fastIO {
	template<class T>
	inline void read(T &x) {
		x=0;
		bool fu=0;
		char ch=0;
		while(ch>'9'||ch<'0') {
			ch=getchar();
			if(ch=='-')fu=1;
		}
		while(ch<='9'&&ch>='0') x=(x*10-48+ch),ch=getchar();
		if(fu)x=-x;
	}
	inline int read() {
		int x=0;
		bool fu=0;
		char ch=0;
		while(ch>'9'||ch<'0') {
			ch=getchar();
			if(ch=='-')fu=1;
		}
		while(ch<='9'&&ch>='0') x=(x*10-48+ch),ch=getchar();
		return fu?-x:x;
	}
	template<class T,class... Args>
	inline void read(T& t,Args&... args) {
		read(t);
		read(args...);
	}
	char _n_u_m_[40];
	template<class T>
	inline void write(T x) {
		if(x==0){
			putchar('0');
			return;
		}
		T tmp = x > 0 ? x : -x ;
		if( x < 0 ) putchar('-') ;
		register int cnt = 0 ;
		while( tmp > 0 ) {
			_n_u_m_[ cnt ++ ] = tmp % 10 + '0' ;
			tmp /= 10 ;
		}
		while( cnt > 0 ) putchar(_n_u_m_[ -- cnt ]) ;
	}
	template<class T>
	inline void write(T x ,char ch) {
		write(x);
		putchar(ch);
	}
}
using namespace fastIO;
#define int long long
vector<pii>a,b,ans;
ll ta,tb;
inline void ac(vector<int>v,ll &ta,vector<pii>&a){
	vector<int>x,y;
	for(auto i:v){
		if((i&3)==(v[0]&3))x.push_back(i);
		else y.push_back(i);
	}
	while(x.size()>1||y.size()>1){
		if(x.size()>1){
			a.emplace_back(x.back(),x[x.size()-2]);
			ll z=x.back()+x[x.size()-2]>>1;
			x.pop_back();x.pop_back();
			if((z&3)==(v[0]&3))x.push_back(z);
			else y.push_back(z);
		}else{
			a.emplace_back(y.back(),y[y.size()-2]);
			ll z=y.back()+y[y.size()-2]>>1;
			y.pop_back();y.pop_back();
			if((z&3)==(v[0]&3))x.push_back(z);
			else y.push_back(z);
		}
	}
	if(x.size()&&y.size())ta=(x[0]+y[0])>>1,a.emplace_back(x[0],y[0]);
	else if(x.size())ta=x[0];
	else ta=y[0];
}
inline void op(vector<pii>ans){
	for(auto i:ans)write(i.first,' '),write(i.second,'\n');
}
inline bool check(vector<int>v,int d){
	if(v.size()<=d)return false;
	vector<int>x,y;
	for(auto i:v){
		if(i>>d&1)x.push_back(i);
		else y.push_back(i);
	}
	if(x.size()&&y.size())return true;
	x.clear(),y.clear();
	return check(v,d+1);
}
inline vector<int>solve(vector<int>v,int d){
	vector<int>x,y,o;
	for(auto i:v){
		if(i>>d&1)x.push_back(i);
		else y.push_back(i);
	}
	if(x.size()&&y.size()){
		int qwq=x.back(),qaq=y.back();
		x.pop_back(),y.pop_back();
		for(auto i:y)x.push_back(i);
		F(i,1,d-1)o.push_back(x.back()),x.pop_back();
		if(x.size()){
			int res;
			ac(x,res,ans);
			o.push_back(res);
		}
		o.push_back(qwq);
		o.push_back(qaq);
		return o;
	}else{
		vector<int>res=solve(v,d+1);
		int x=res.back(),y=res[res.size()-2];
		res.pop_back(),res.pop_back();
		ans.emplace_back(x,y);
		res.push_back((x+y)>>1);
		return solve(res,d);
	}
}
inline vector<pii>dfs(vector<int>res){//for(auto i:res)cerr<<i<<" ";cerr<<endl;
	if(res.size()==2){
		if((res[0]+res[1])&1)return {};
		else return {{res[0],res[1]}};
	}
	F(i,0,res.size()-1)F(j,i+1,res.size()-1){
		if((res[i]+res[j]+1)&1){
			int x=res[i],y=res[j];
			vector<int>temp=res;
			temp.erase(temp.begin()+j);
			temp.erase(temp.begin()+i);
			temp.push_back((x+y)>>1);
			auto r=dfs(temp);
			if(r.size()){
				r.insert(r.begin(),make_pair(x,y));
				return r;
			}
		}
	}
	return {};
}
signed main() {
	F(asdf,1,read()){
		a.clear(),b.clear(),ans.clear();
		ta=tb=0;
		vector<ll>x,y;
		F(i,1,read()){
			ll v;read(v);
			if(v&1)x.push_back(v);
			else y.push_back(v);
		}
		if(y.empty()){
			ac(x,ta,a);
			op(a);
			continue;
		}
		if(x.empty()){
			ac(y,tb,b);
			op(b);
			continue;
		}
		sort(x.begin(),x.end());
		sort(y.begin(),y.end());
		if(check(x,1)){
			vector<int>res=solve(x,1);
			if(res.size()==2){
				ans.emplace_back(res[0],res[1]);
				y.push_back((res[0]+res[1])>>1);
				ac(y,tb,ans);
				op(ans);
				continue;
			}else{
				ac(y,tb,ans);
				res.push_back(tb);
				op(ans);
				op(dfs(res));
			}
		}else if(check(y,1)){
			vector<int>res=solve(y,1);
			if(res.size()==2){
				ans.emplace_back(res[0],res[1]);
				x.push_back((res[0]+res[1])>>1);
				ac(x,ta,ans);
				op(ans);
				continue;
			}else{
				ac(x,ta,ans);
				res.push_back(ta);
				op(ans);
				op(dfs(res));
			}
		}else{
			puts("-1");
		}
	}
	return 0;
}
/*
114514
4
1 3 5 2
*/