#include<bits/stdc++.h>
#define Gc() getchar()
#define Me(x,y) memset(x,y,sizeof(x))
#define Mc(x,y) memcpy(x,y,sizeof(x))
#define d(x,y) ((m)*(x-1)+(y))
#define R(n) (rnd()%(n)+1)
#define Pc(x) putchar(x)
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define eb emplace_back
#define all(x) x.begin(),x.end()
using namespace std;using ll=long long;using db=double;using lb=long db;using ui=unsigned;using ull=unsigned long long;using pii=pair<int,int>;
const int N=1e6+5,M=N*8+5,K=1000+5,mod=1e9+9,Mod=mod-1;const db eps=1e-8;const int INF=1e9+7;mt19937 rnd(263082);
#define Tp template<typename T>
#define Ts template<typename T,typename... Ar>
namespace Debug{
	Tp void _debug(char* f,T t){cerr<<f<<'='<<t<<endl;}
	Ts void _debug(char* f,T x,Ar... y){while(*f!=',') cerr<<*f++;cerr<<'='<<x<<",";_debug(f+1,y...);}
	#ifdef LOCAL
	#define gdb(...) _debug((char*)#__VA_ARGS__,__VA_ARGS__)
	#else 
	#define gdb(...) void()
	#endif
}using namespace Debug;
int n,vis[N];ll A[N];
queue<ll> q[3];
ll a1[N],a2[N];int ah;
void add(ll x){
	if(!q[x&1].empty()){
		ll y=q[x&1].front();
		a1[++ah]=x;a2[ah]=y;
		q[x&1].pop();
		add(x+y>>1);
	}else q[x&1].emplace(x);
}
void Solve(){
	int i,j;scanf("%d",&n);
	for(i=1;i<=n;i++) scanf("%lld",&A[i]);
	int k=350;
	while(k--){
		shuffle(A+1,A+n+1,rnd);ah=0;
		for(int o:{0,1}) q[o]=q[2];
		for(i=1;i<=n;i++) add(A[i]);
		if(ah==n-1){
			for(i=1;i<=ah;i++) printf("%lld %lld\n",a1[i],a2[i]);
			return;
		}
	}
	puts("-1");
}
int main(){
    int t=1;
    scanf("%d",&t);
    while(t--) Solve();
    cerr<<clock()*1.0/CLOCKS_PER_SEC<<'\n';
}