#include <iostream>

#include <queue>

#include <vector>

#include <memory.h>

using namespace std;

typedef pair<int, int> p;

priority_queue<p, vector<p>, greater<p>> pq;

vector< vector<p> > edge;

int vals[20001];

bool vis[20001];

void dijkstra(int start)

{

	vals[start] = 0;

	pq.push({ 0, start });

	while (!pq.empty())

	{

		auto [val, u] = pq.top();

		pq.pop();

		vis[u] = true;

		for (auto& [v, w] : edge[u]) if (!vis[v])

		{

			int tmp = val + w;

			if (vals[v] == -1 || vals[v] > tmp)

			{

				vals[v] = tmp;

				pq.push({ tmp, v });

			}

		}

	}

}

int main()

{

	// fast io

	ios::sync_with_stdio(false);

	cin.tie(nullptr);

	cout.tie(nullptr);

	int T, cases = 0;

	cin >> T;

	while (T--)

	{

		int n, m, s, t;

		cin >> n >> m >> s >> t;

		// init

		edge.assign(n, vector<p>());

		memset(vals, -1, sizeof(vals));

		memset(vis, false, sizeof(vis));

		// store data in both side

		while (m--)

		{

			int u, v, w;

			cin >> u >> v >> w;

			edge[u].push_back({ v, w });

			edge[v].push_back({ u, w });

		}

		// dijkstra algorithm

		dijkstra(s);

		cout << "Case #" << ++cases << ": ";

		if (vals[t] == -1) cout << "unreachable\n";

		else cout << vals[t] << "\n";

	}

	return 0;

}