#include<bits/stdc++.h>
using namespace std;

#define rep(i,a,b) for(int i=(a),i##end=(b);i<=i##end;++i)
#define per(i,a,b) for(int i=(a),i##end=(b);i>=i##end;--i)
mt19937 Rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
template<typename T>void chkmax(T&x,const T&y){if(x<y)x=y;}
template<typename T>void chkmin(T&x,const T&y){if(y<x)x=y;}

#define pb push_back
#define ALL(x) (x).begin(),(x).end()
#define mem(x) memset((x),0,sizeof(x))

typedef double db;
typedef long long ll;
typedef vector<int>vi;
typedef pair<int,int>pii;

typedef unsigned u32;
typedef unsigned uint;
typedef unsigned long long u64;

namespace orzjk{
  const int SZ=1e6;
  char buf[SZ],*p1=buf,*p2=buf;
  char nc(){
    return p1==p2&&(p2=(p1=buf)+fread(buf,1,SZ,stdin),p1==p2)?EOF:*p1++;
  }
  char fub[SZ],*p3=fub,*p4=fub+SZ;
  void pc(char c){
    p3==p4&&(fwrite(fub,1,SZ,stdout),p3=fub);
    *p3++=c;
  }
  void flush(){
    fwrite(fub,1,p3-fub,stdout),p3=fub;
  }
}
using orzjk::nc;
using orzjk::pc;

//#define nc getchar
//#define pc putchar

ll read(){
  ll x=0,f=1;char c=nc();
  while(c<48)c=='-'&&(f=-1),c=nc();
  while(c>47)x=x*10+(c^48),c=nc();
  return x*f;
}
template<class T>void write(T x){
  static char st[41];
  if(!x)return pc(48),void();
  char*p=st;
  if(x<0)x=-x,pc('-');
  for(;x;x/=10)*p++=x%10|48;
  do{
    pc(*--p);
  }while(p!=st);
}

//const int P=1e9+7;
const int P=998244353;
int qp(int a,int k){
  int res=1;for(;k;k>>=1,a=1ll*a*a%P)if(k&1)res=1ll*res*a%P;return res;
}

bool asf;
typedef vector<ll>vl;
typedef pair<ll,ll>pr;
vector<pr>out;
void dfs(vl a){
  if(a.size()==1u){
    asf=1;
    for(auto[a,b]:out){
      write(a),pc(32),write(b),pc(10);
    }
    return;
  }
  sort(ALL(a));
  rep(i,0,a.size()-1)rep(j,i+1,a.size()-1)if((a[i]+a[j])%2==0){
    out.pb({a[i],a[j]});
    vl b=a;
    b.erase(b.begin()+j);
    b.erase(b.begin()+i);
    b.pb((a[i]+a[j])/2);
    dfs(b);
    if(asf)return;
    out.pop_back();
  }
}

const int maxn=1e6+10;
int n;
ll a[maxn];

void solve(){
  n=read();
  bool ev=1;
  rep(i,1,n)a[i]=read(),ev&=a[i]%2==0;
  if(ev){
    ll v[2]={-1,-1};
    auto push=[&](ll x){
      while(1){
        int c=x>>1&1;
        if(v[c]==-1){
          v[c]=x;return;
        }
        ll y=v[c];
        v[c]=-1;
        write(x),pc(32),write(y),pc(10);
        x=(x+y)/2;
      }
    };
    rep(i,1,n)push(a[i]);
    if(v[0]!=-1&&v[1]!=-1){
      write(v[0]),pc(32),write(v[1]),pc(10);
    }
    return;
  }
  if(n<=7){
    vl v(n);
    rep(i,0,n-1)v[i]=a[i+1];
    asf=0;
    out.clear();
    dfs(v);
    if(!asf)write(-1),pc(10);
  }
}

signed main(){
//  freopen(".in","r",stdin);
//  freopen(".out","w",stdout);
  int T;cin>>T;while(T--)solve();
//  solve();
  orzjk::flush();
  return 0;
}