// what is matter? never mind. 
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,sse4,popcnt,abm,mmx,avx,avx2") 
#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rep(i,a,b) for(int i=(a);i>=(b);--i)
#define ll long long
#define int long long
#define ull unsigned long long
#define SZ(x) ((int)((x).size()))
#define ALL(x) (x).begin(),(x).end()
using namespace std;
inline int read()
{
    char c=getchar();int x=0;bool f=0;
    for(;!isdigit(c);c=getchar())f^=!(c^45);
    for(;isdigit(c);c=getchar())x=(x<<1)+(x<<3)+(c^48);
    if(f)x=-x;return x;
}

#define fi first
#define se second
#define pb push_back
#define mkp make_pair
typedef pair<int,int>pii;
typedef vector<int>vi;

#define maxn 1000006
#define inf 0x3f3f3f3f

int n,a[maxn];
vi t[2];

mt19937_64 rnd(time(0));

bool solve(){
	vector<pii>res;
	while(t[0].size()+t[1].size()>1){
		if(SZ(t[0])==1 && SZ(t[1])==1) return 0;
		int o=rnd()&1;
		For(i,0,1)
			if(SZ(t[o^i])>1){
				int a=t[o^i].back(); t[o^i].pop_back();
				int b=t[o^i].back(); t[o^i].pop_back();
				res.pb(mkp(a,b));
				a=(a+b)/2;
				t[a&1].pb(a);
			}
	}
	for(auto [x,y]:res) cout<<x<<" "<<y<<"\n";
	return 1;
}

void work()
{
	n=read();
	For(i,1,n)a[i]=read();
	For(_,1,500){
		For(i,0,1) t[i].clear();
		For(i,1,n) t[a[i]&1].pb(a[i]);
		if(solve()){
			return;
		}
		shuffle(a+1,a+n+1,rnd);
	}
	puts("-1");
}

signed main()
{
	int T=read();
	while(T--)work();
	return 0;
}

/*
*/