#include<bits/stdc++.h>
#define pd push_back
#define all(A) A.begin(),A.end()
#define lb lower_bound
#define ve std::vector
typedef long long ll;
typedef long long ll;
typedef __int128 Int;
typedef unsigned long long ul;
typedef long double LD;
bool FileIfstream(std::string name){
	std::ifstream f(name.c_str());
	return f.good();
}
namespace Math{
	ll QP(ll x,ll y,ll mod){ll ans=1;for(;y;y>>=1,x=x*x%mod)if(y&1)ans=ans*x%mod;return ans;}
	ll inv(ll x,ll mod){return QP(x,mod-2,mod);}
}
const int N=2e5+10;
const int mod=998244353;
std::mt19937_64 rnd(time(NULL));
ul Grnd(ul l,ul r){
	return rnd()%(r-l+1)+l;
}
void solve(){
	//don't forget to open long long
	int n;std::cin>>n;
	ve<ll>v(n+1);
	for(int i=1;i<=n;i++)
		std::cin>>v[i];
	int T=400;
	while(T--){
		ve<std::array<ll,2>>ans; 
		shuffle(v.begin()+1,v.end(),rnd);
		ve<ll>C[2];
		for(int i=1;i<=n;i++)C[v[i]&1].pd(v[i]);
		bool flg=true;
		for(int i=1;i<n;i++){
			ll p=rnd()&1;
			if(C[p].size()<=1)p^=1;
			if(C[p].size()==1){flg=false;break;}
			ll x=C[p].back();C[p].pop_back();
			ll y=C[p].back();C[p].pop_back();
			ans.pd({x,y});
			x=(x+y)/2;
			C[x&1].pd(x);
		}
		if(flg){
			for(auto &p:ans)
				std::cout<<p[0]<<' '<<p[1]<<'\n';
				return;
		}
	}
	std::cout<<-1<<'\n';
}
int main(){
#ifndef ONLINE_JUDGE
	if(!FileIfstream("IO.in")){
		freopen("IO.in","w",stdout);
		return 0;
	}
	freopen("IO.in","r",stdin);
	freopen("IO.out","w",stdout);
#endif
	std::ios::sync_with_stdio(false);
	std::cin.tie(0);
	std::cout.tie(0);
	int T=1;
	std::cin>>T;
	while(T--)solve();

#ifndef ONLINE_JUDGE
	std::cerr<<std::fixed<<std::setprecision(10)<<1.0*clock()/CLOCKS_PER_SEC<<'\n';
#endif

	return 0;
}