#include <iostream>
#include <set>
using namespace std;
 
multiset <pair <unsigned int, unsigned int>> M;
multiset <pair <unsigned int, unsigned int>>::iterator it;
 
int main() {
	unsigned int t, n, a, b;
	cin >> t;
	while (t != 0) {
		cin >> n;
		M.clear();
		for (int i = 0; i < n; i++) {
			cin >> a >> b;
			if ((it = M.find (make_pair(b, a))) == M.end()) {
				M.insert (make_pair(a, b));
			} else M.erase(it);
		}
		(M.empty()) ? cout << "YES" << endl : cout << "NO" << endl;
		t--;
	}
 
	return 0;
}

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