# include <bits/stdc++.h>
using namespace std;
typedef long long ll;
vector<ll> A[70];
queue<int> que;
bool vis[70];
int V2(ll x){return __builtin_ctzll(x);}
int main()
{
	int T;
	cin>>T;
	while(T--)
	{
		int n;
		ll x;
		scanf("%d",&n);
		for(int i=1;i<=n;i++) scanf("%lld",&x),A[V2(x)].push_back(x);
		auto Push=[&](int i){if(A[i].size()>1 && !vis[i]) vis[i]=1,que.push(i);};
		for(int i=1;i<60;i++)
			if(A[i].size()>1) que.push(i),vis[i]=1;
		while(!que.empty())
		{
			int u=que.front(),v;que.pop();
			vis[u]=0;
			ll x,y;
			x=A[u].back();A[u].pop_back();
			y=A[u].back();A[u].pop_back();
			printf("%lld %lld\n",x,y);
			A[v=V2((x+y)/2)].push_back((x+y)/2);
			Push(u);Push(v);
		}
		ll lst=-1;
		for(int i=59;i>=1;i--)
			if(!A[i].empty())
			{
				if(lst<0) lst=A[i][0];
				else printf("%lld %lld\n",lst,A[i][0]),lst=(lst+A[i][0])/2;
			}
		for(int i=1;i<60;i++) A[i].clear();
	}
	return 0;
}