#include <bits/stdc++.h>

using namespace std;

#define rep(i, a, b)	for (int i(a); i <= (b); ++i)

#define dec(i, a, b)	for (int i(a); i >= (b); --i)

#define MP		make_pair

#define fi		first

#define se		second

typedef long long LL;

typedef pair <int, int> PII;

const int N = 1e5 + 10;

int T;

int n;

int x[N], y[N];

int p, q;

int cnt;

vector <int> a[2][2];

vector <PII> ans;

map <PII, int> mp;

int main(){

	scanf("%d", &T);

	while (T--){

		scanf("%d", &n);

		ans.clear();

		mp.clear();

		rep(i, 0, 1) rep(j, 0, 1) a[i][j].clear();

		rep(i, 1, n){

			scanf("%d%d", x + i, y + i);

			a[abs(x[i]) & 1][abs(y[i]) & 1].push_back(i);

		}

		p = 0, q = 0;

		rep(i, 0, 1) rep(j, 0, 1){

			if (a[i][j].size() > a[p][q].size()){

				p = i;

				q = j;

			}

		}

		cnt = n / 10;

		rep(i, 0, a[p][q].size() - 2){

			rep(j, i + 1, a[p][q].size() - 1){

				int l = a[p][q][i], r = a[p][q][j];

				if ((l + 1 == r) || (l == 1 && r == n)) continue;

				int nx = (x[l] + x[r]) >> 1;

				int ny = (y[l] + y[r]) >> 1;

				if (!mp.count(MP(nx, ny))){

					ans.push_back(MP(nx, ny));

					mp[MP(nx, ny)] = 1;

					--cnt;

				}

				if (cnt == 0) break;

			}

			if (cnt == 0) break;

		}

		for (auto u : ans) printf("%d %d\n", u.fi, u.se);

	}

	return 0;

}