#include <iostream>

#include <vector>

using namespace std;

vector<int> sent;

vector<bool> check, sum;

int times;

void dfs(int num)

{

	++times;

	sum[num] = check[num] = true;

	if (!check[sent[num]]) dfs(sent[num]);

}

int main()

{

	ios::sync_with_stdio(false);

	cin.tie(nullptr);

	cout.tie(nullptr);

	int T, N;

	cin >> T;

	for (int i = 1; i <= T; ++i) {

		cin >> N;

		sent.assign(N + 1, -1);

		sum.assign(N + 1, false);

		for (int j = 0, a, b; j < N; ++j) cin >> a >> b, sent[a] = b;

		int ftimes = 1;

		int fnum = sent[0];

		for (int j = 1; j <= N; ++j)

			if (!sum[j]) {

				check.assign(N + 1, false);

				check[j] = true;

				times = 1;

				dfs(sent[j]);

				if (times > ftimes || (times == ftimes && j < fnum))

					fnum = j, ftimes = times;

			}

		cout << "Case " << i << ": " << fnum << "\n";

	}

	return 0;

}