#include<bits/stdc++.h>

#define pb push_back
#define fi first
#define se second
#define mp make_pair

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef long double ld;

template <typename T> bool chkmin(T &x,T y){return x>y?x=y,1:0;}
template <typename T> bool chkmax(T &x,T y){return x<y?x=y,1:0;}

ll readint(){
	ll x=0,f=1; char ch=getchar();
	while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
	while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
	return x*f;
}

int n;
ll a[1000005];
vector<ll> b[3][10];
vector<pll> ans;

bool solve(vector<ll> vec){
	if(vec.size()==1) return true;
	for(int i=0;i<vec.size();i++){
		for(int j=i+1;j<vec.size();j++){
			if((vec[i]+vec[j])%2) continue;
			vector<ll> th;
			for(int k=0;k<vec.size();k++) if(k!=i&&k!=j) th.pb(vec[k]);
			th.pb((vec[i]+vec[j])/2);
			if(solve(th)){
				ans.pb(mp(vec[i],vec[j]));
				return true;
			}
		}
	}
	return false;
}

void solve(){
	for(int i=1;i<=n;i++) a[i]=readint();
	b[2][0].clear(),b[2][2].clear();
	for(int i=1;i<=n;i++) if(a[i]%2==0) b[2][a[i]%4].pb(a[i]);
	for(int i=1;i<n;i++){
		if(b[2][0].size()>=2){
			ll x=b[2][0].back(); b[2][0].pop_back();
			ll y=b[2][0].back(); b[2][0].pop_back();
			printf("%lld %lld\n",x,y);
			b[2][(x+y)/2%4].pb((x+y)/2);
		}
		else if(b[2][2].size()>=2){
			ll x=b[2][2].back(); b[2][2].pop_back();
			ll y=b[2][2].back(); b[2][2].pop_back();
			printf("%lld %lld\n",x,y);
			b[2][(x+y)/2%4].pb((x+y)/2);
		}
		else printf("%lld %lld\n",b[2][0][0],b[2][2][0]);
	}
}

int main(){
	int T=readint();
	while(T--){
		n=readint();
		if(n<=7){
			vector<ll> vec(0);
			for(int i=1;i<=n;i++) vec.pb(readint());
			ans.clear();
			if(!solve(vec)) printf("-1\n");
			else{
				reverse(ans.begin(),ans.end());
				for(auto r:ans) printf("%lld %lld\n",r.fi,r.se);
			}
		}
		else{
			solve();
		}
	}
	return 0;
}