//Author: Kevin5307
#include<bits/stdc++.h>
//#pragma GCC optimize("O2")
using namespace std;
#define ll long long
#define int ll
#define ull unsigned ll
#define pb push_back
#define mp make_pair
#define ALL(x) (x).begin(),(x).end()
#define rALL(x) (x).rbegin(),(x).rend()
#define srt(x) sort(ALL(x))
#define rev(x) reverse(ALL(x))
#define rsrt(x) sort(rALL(x))
#define sz(x) (int)(x.size())
#define inf 0x3f3f3f3f
#define pii pair<int,int>
#define lb(v,x) (int)(lower_bound(ALL(v),x)-v.begin())
#define ub(v,x) (int)(upper_bound(ALL(v),x)-v.begin())
#define uni(v) v.resize(unique(ALL(v))-v.begin())
#define longer __int128_t
void die(string S){puts(S.c_str());exit(0);}
vector<pii> cur;
bool dfs(vector<int> vec)
{
	if(sz(vec)==1)
	{
		for(auto pr:cur)
			printf("%lld %lld\n",pr.first,pr.second);
		return true;
	}
	for(int i=0;i<sz(vec);i++)
		for(int j=i+1;j<sz(vec);j++)
			if((vec[i]+vec[j])%2==0)
			{
				vector<int> nvec;
				for(int k=0;k<sz(vec);k++)
					if(k!=i&&k!=j)
						nvec.pb(vec[k]);
				nvec.pb((vec[i]+vec[j])/2);
				cur.pb(mp(vec[i],vec[j]));
				if(dfs(nvec))
					return true;
				cur.pop_back();
			}
	return false;
}
signed main()
{
	int t;
	scanf("%lld",&t);
	while(t--)
	{
		int n;
		scanf("%lld",&n);
		vector<int> vec;
		bool flag=1;
		for(int i=1;i<=n;i++)
		{
			int x;
			scanf("%lld",&x);
			vec.pb(x);
			if(x%2)
				flag=0;
		}
		if(flag)
		{
			set<int> st[2];
			for(auto x:vec)
				st[x/2%2].insert(x);
			for(int i=2;i<n;i++)
			{
				if(sz(st[0])>1)
				{
					int x=*st[0].begin();
					st[0].erase(st[0].begin());
					int y=*st[0].begin();
					st[0].erase(st[0].begin());
					int z=(x+y)/2;
					printf("%lld %lld\n",x,y);
					st[z/2%2].insert(z);
				}
				else
				{
					int x=*st[1].begin();
					st[1].erase(st[1].begin());
					int y=*st[1].begin();
					st[1].erase(st[1].begin());
					int z=(x+y)/2;
					printf("%lld %lld\n",x,y);
					st[z/2%2].insert(z);
				}
			}
			vector<int> vec;
			for(auto x:st[0])
				vec.pb(x);
			for(auto y:st[1])
				vec.pb(y);
			printf("%lld %lld\n",vec[0],vec[1]);
		}
		else if(n<=7)
		{
			cur.clear();
			if(!dfs(vec))
				puts("-1");
		}
	}
	return 0;
}