#include<bits/stdc++.h>
using namespace std;
using ll=long long;
using ull=unsigned long long;
#define all(x) (x).begin(),x.end()
template<class T>
auto ary(T *a,int l,int r){
	return vector<T>{a+l,a+1+r};
}
template<class T>
auto each(int l,int r,const T &f){
	auto x=f(l);
	vector<decltype(x)>t{x};
	for(int i=l+1;i<=r;i++)t.push_back(f(i));
	return t;
}
template<bool x>
using If=typename enable_if<x>::type;
template<int i,class T>
If<i==0> otp(ostream &out,T a){
	out<<get<i>(a);
}
template<int i,class T>
If<i!=0> otp(ostream &out,T a){
	otp<i-1>(out,a),out<<','<<get<i>(a);
}
template<class T>
ostream& operator << (ostream &out,vector<T> a);
template<class...T>
ostream& operator << (ostream &out,tuple<T...>a){
	return out<<'(',otp<sizeof...(T)-1>(out,a),out<<')';
}
template<class T>
ostream& operator << (ostream &out,vector<T> a){
	out<<'[';
	for(auto x:a)out<<x<<',';
	return out<<']';
}
#ifdef DEBUG
template<class T>
void debug(T x){
	cerr<<x<<endl;
}
template<class T,class...S>
void debug(T x,S...y){
	cerr<<x<<' ',debug(y...);
}
#else
#define debug(...) void()
#endif
const int N=1e6+10;
int T,n;
ll b[N];
int cnt;
pair<ll,ll>ans[N];
ll v[2][N];
int t[2];
mt19937 rnd(time(0));
void push(ll x){
	v[x&1][++t[x&1]]=x;
}
bool run(){
	t[0]=t[1]=0;
	for(int i=1;i<=n;i++)push(b[i]);
	shuffle(b+1,b+1+n,rnd);
	int k=n;
	cnt=0;
	for(;k>1;k--){
		int c=rnd()%2;
		if(t[c]<2)c^=1;
		if(t[c]<2)return 0;
		int len=t[c];
		ll x=v[c][len-1],y=v[c][len];
		ans[++cnt]={x,y};
		t[c]-=2;
		push((x+y)/2);
	}
	for(int i=1;i<=cnt;i++){
		auto [x,y]=ans[i];
		printf("%lld %lld\n",x,y);
	}
	return 1;
}
void get(){
	scanf("%d",&n);
	for(int i=1;i<=n;i++)scanf("%lld",&b[i]);
	for(int T=400;T--;)if(run())return;
	puts("-1");
}
int main(){
	// freopen("cow.in","r",stdin);
	// freopen("cow.out","w",stdout);
	for(scanf("%d",&T);T--;)get();
	return 0;
}