#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=1e6+10;
mt19937 rnd(time(0));
vector<ll> t[2];
vector<pair<ll,ll>> v;
ll a[N];
int n,T;
ll Pop(int x){
	ll a=t[x].back();
	t[x].pop_back();
	return a;
}
void work(int j){
	ll x=Pop(j),y=Pop(j),z=(x+y)>>1;
	v.push_back({x,y});
	t[z&1].push_back(z);
}
bool okok(){
	v.clear();
	for(int i=0;i<2;i++) t[i].clear();
	for(int i=1;i<=n;i++) t[a[i]&1].push_back(a[i]);
	for(int i=1;i<n;i++){
		if(t[0].size()==1 && t[1].size()==1) return 0;
		int p=rnd()&1;
		for(int j=0;j<2;j++)
			if(t[j^p].size()>1){work(j^p);break;}
	}
	for(auto k:v) printf("%lld %lld\n",k.first,k.second);
	return 1;
}
int main(){
//	freopen("meow.in","r",stdin);
//	freopen("meow.out","w",stdout);
	scanf("%d",&T);
	while(T--){
		scanf("%d",&n);
		for(int i=1;i<=n;i++)
			scanf("%lld",&a[i]);
		int flag=0;
		for(int i=1;i<=500;i++){
			shuffle(a+1,a+n+1,rnd);
			if(okok()) {flag=1;break;}
		}
		if(!flag) puts("-1");
	}
	return 0;
}