#include<bits/stdc++.h>
using namespace std;
int T,n;
vector<long long>f[2];
long long print(long long x,long long y){assert(x+y+1&1);cout<<x<<' '<<y<<'\n';return x+y>>1;}
void add(long long w){
	if(f[w>>1&1].size()){
		long long t=print(w,f[w>>1&1].back());
		f[w>>1&1].pop_back();add(t);
	}else f[w>>1&1].push_back(w);
}
void solve(vector<long long>t){
	f[0].clear();f[1].clear(); 
	for(auto i:t)add(i);
	if(f[0].size()&&f[1].size())print(f[0][0],f[1][0]);
}
void ins(long long w){
	if(f[w&1].size()){
		long long t=print(w,f[w&1].back());
		f[w&1].pop_back();ins(t);
	}else f[w&1].push_back(w);
}
void rebuild(vector<long long>t){
	f[0].clear();f[1].clear(); 
	for(auto i:t)ins(i);
}
vector<long long>C;
bool check(vector<long long>&v){
	int minn=70,j=0;
	for(int i=1;i<v.size();i++)
		if(v[i]!=v[0]&&__builtin_ctzll(v[i]^v[0])<minn)
			j=i,minn=__builtin_ctzll(v[i]^v[0]);
	if(!j||v.size()<minn+1){for(auto i:v)C.push_back(i);v={};return 0;}
	long long x=v[0],y=v[j];
	v.erase(v.begin()+j);v.erase(v.begin());
	for(int i=0;i<minn-1;i++)
		x=print(x,y),y=v.back(),v.pop_back();
	for(auto i:v)C.push_back(i);
	v={x,y};return 1;
}
vector<pair<long long,long long> >H;
bool DFS(vector<long long>V){
	if(V.size()==1)return 1;
	for(int i=0;i<V.size();i++)
		for(int j=i+1;j<V.size();j++)
			if(V[i]+V[j]+1&1){
				vector<long long>G=V;
				G.erase(G.begin()+j);
				G.erase(G.begin()+i);
				G.push_back({V[i]+V[j]>>1});
				H.push_back({V[i],V[j]});
				if(DFS(G))return 1;
				H.pop_back();
			}
	return 0;
}
void force(vector<long long>V){
	H.clear();assert(DFS(V));
	for(auto i:H)cout<<i.first<<' '<<i.second<<'\n';
}
int main(){
	ios::sync_with_stdio(0);
	cin.tie(NULL);
	cout.tie(NULL);
	cin>>T;
	while(T--){
		cin>>n;
		vector<long long>v[2];
		for(int i=0;i<n;i++){
			long long a;cin>>a;
			v[a&1].push_back(a);
		}
		if(v[0].size()==n){solve(v[0]);continue;}
		if(v[1].size()==n){solve(v[1]);continue;}
		C.clear();
		if(check(v[0])||check(v[1])){
			if(v[1].size()>2){
				for(auto i:v[1])
					C.push_back(i);
				v[1]={};
			}	
			rebuild(C);
			vector<long long>V;
			for(auto i:v[0])V.push_back(i);
			for(auto i:v[1])V.push_back(i);
			for(auto i:f[0])V.push_back(i);
			for(auto i:f[1])V.push_back(i);
			force(V);
		}else
			cout<<"-1\n";
	}
}