#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,cnt;
ll a[2000005];
bool vis[2000005];
vector<ll> b[20][10005];
vector<pll> c[4],ans;

pll merge(pll x,pll y){
	ll res=(x.fi+y.fi)/2;
	ans.pb(mp(x.fi,y.fi));
	vis[x.se]=vis[y.se]=1;
	a[++cnt]=res;
	return mp(res,cnt);
}

void solve(){
	ans.clear();
	n=readint();
	for(int i=1;i<=n+n;i++) vis[i]=0;
	for(int i=0;i<4;i++) b[2][i].clear();
	for(int i=0;i<4;i++) c[i].clear();
	cnt=n;
	for(int i=1;i<=n;i++) a[i]=readint();
	for(int i=1;i<=n;i++) b[2][a[i]%4].pb(a[i]);
	if(!b[2][0].size()&&!b[2][2].size()){
		for(int i=1;i<n;i++){
			if(b[2][1].size()>=2){
				ll x=b[2][1].back(); b[2][1].pop_back();
				ll y=b[2][1].back(); b[2][1].pop_back();
				printf("%lld %lld\n",x,y);
				b[2][(x+y)/2%4].pb((x+y)/2);
			}
			else if(b[2][3].size()>=2){
				ll x=b[2][3].back(); b[2][3].pop_back();
				ll y=b[2][3].back(); b[2][3].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][1][0],b[2][3][0]);
		}
		return;
	}
	if(!b[2][0].size()||!b[2][2].size()){
		int lst=b[2][0].size()?0:2;
		vector<pll> vec;
		for(int i=1;i<=n;i++) if(a[i]&1) vec.pb(mp(a[i],i));
		for(int i=2;i<=60;i++){
			vector<pll> tmp[2];
			for(auto r:vec){
				if(vis[r.se]) continue;
				tmp[(r.fi>>(i-1))&1].pb(r);
			}
			if(tmp[0].size()&&tmp[1].size()){
				if(i>2){
					vec.pb(merge(tmp[0][0],tmp[1][0]));
					i-=2;
				}
				else{
					while(1){
						if(tmp[0].size()>=2){
							pll x1=tmp[0].back(); tmp[0].pop_back();
							pll x2=tmp[0].back(); tmp[0].pop_back();
							pll y=tmp[1].back(); tmp[1].pop_back();
							if((x1.fi+y.fi)/2%4!=lst){
								merge(x1,y);
								break;
							}
							else if((x2.fi+y.fi)/2%4!=lst){
								merge(x2,y);
								break;
							}
							else{
								tmp[1].pb(y);
								tmp[0].pb(merge(x1,x2));
							}
						}
						else if(tmp[1].size()>=2){
							pll x1=tmp[1].back(); tmp[1].pop_back();
							pll x2=tmp[1].back(); tmp[1].pop_back();
							pll y=tmp[0].back(); tmp[0].pop_back();
							if((x1.fi+y.fi)/2%4!=lst){
								merge(x1,y);
								break;
							}
							else if((x2.fi+y.fi)/2%4!=lst){
								merge(x2,y);
								break;
							}
							else{
								tmp[0].pb(y);
								tmp[1].pb(merge(x1,x2));
							}
						}
						else{
							merge(tmp[0][0],tmp[1][0]);
							break;
						}
					}
					break;
				}
			}
			if(i==60) return (void)(printf("-1\n"));
		}
	}
	// cout<<"test ";
	// for(int i=1;i<=cnt;i++) if(!vis[i]) cout<<a[i]<<' ';
	// cout<<endl;
	int rt=0;
	for(int i=1;i<=cnt;i++) if(!vis[i]&&a[i]%2==1) rt=i;
	if(rt){
		for(int i=1;i<=cnt;i++) if(!vis[i]&&a[i]%2==1) c[a[i]%4].pb(mp(a[i],i));
		while(1){
			if(c[1].size()+c[3].size()<=1) break;
			if(c[1].size()>=2){
				pll x=c[1].back(); c[1].pop_back();
				pll y=c[1].back(); c[1].pop_back();
				c[(x.fi+y.fi)/2%4].pb(merge(x,y));
			}
			else if(b[2][3].size()>=2){
				pll x=c[3].back(); c[3].pop_back();
				pll y=c[3].back(); c[3].pop_back();
				c[(x.fi+y.fi)/2%4].pb(merge(x,y));
			}
			else{
				merge(c[1][0],c[3][0]);
				break;
			}
		}
	}
	rt=0;
	for(int i=1;i<=cnt;i++) if(!vis[i]&&a[i]%2==1) rt=i;
	if(rt){
		for(int i=0;i<4;i++) c[i].clear();
		for(int i=1;i<=cnt;i++){
			if(vis[i]) continue;
			c[a[i]%4].pb(mp(a[i],i));
		}
		int lst=c[1].size()?1:3;
		pll fin=mp(0,0),ed=mp(0,0);
		while(1){
			if(c[0].size()>=2){
				pll x1=c[0].back(); c[0].pop_back();
				pll x2=c[0].back(); c[0].pop_back();
				pll y=c[2].back(); c[2].pop_back();
				if((x1.fi+y.fi)/2%4!=lst){
					fin=merge(x1,y);
					break;
				}
				else if((x2.fi+y.fi)/2%4!=lst){
					fin=merge(x2,y);
					break;
				}
				else{
					c[2].pb(y);
					c[0].pb(merge(x1,x2));
				}
			}
			else if(c[2].size()>=2){
				pll x1=c[2].back(); c[2].pop_back();
				pll x2=c[2].back(); c[2].pop_back();
				pll y=c[0].back(); c[0].pop_back();
				if((x1.fi+y.fi)/2%4!=lst){
					fin=merge(x1,y);
					break;
				}
				else if((x2.fi+y.fi)/2%4!=lst){
					fin=merge(x2,y);
					break;
				}
				else{
					c[0].pb(y);
					c[2].pb(merge(x1,x2));
				}
			}
			else{
				ed=merge(c[0][0],c[2][0]);
				break;
			}
		}
		if(fin.se){
			if(c[1].size()) merge(c[1][0],fin);
			else merge(c[3][0],fin);
		}
		else{
			if(c[1].size()) merge(c[1][0],ed);
			else merge(c[3][0],ed);
		}
	}
	b[2][0].clear(),b[2][2].clear();
	for(int i=1;i<=cnt;i++){
		if(vis[i]) continue;
		b[2][a[i]%4].pb(a[i]);
	}
	// cout<<"test ";
	// for(int i=1;i<=cnt;i++) if(!vis[i]) cout<<a[i]<<' ';
	// cout<<endl;
	for(auto r:ans) printf("%lld %lld\n",r.fi,r.se);
	while(1){
		if(b[2][0].size()+b[2][2].size()==1) break;
		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]);
			break;
		}
	}
}

int main(){
	int T=readint();
	while(T--) solve();
	return 0;
}