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#include <vector>
#include <list>
#include <queue>
using namespace std;
template<typename T>
using Matrix = vector<list<T>>;
constexpr int INF = 100000;
struct
{
int idx;
int weight;
Edge(int i = -1, int w = INF) : idx{ i }, weight{ w } {}
};
inline bool operator<(const Edge &lhs, const Edge &rhs)
{
return lhs.weight > rhs.weight;
}
class Solution
{
public:
Solution()
{
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
}
int calculate(const Matrix<Edge> &w, const int Vertices, const int start, const int end)
{
initialize(Vertices);
priority_queue<Edge> que;
int min_idx = start;
dist[min_idx] = 0;
que.push({ min_idx,0 });
while (true)
{
min_idx = get_min_edge(que);
if (min_idx == end || min_idx == -1)
break;
checked[min_idx] = true;
relax(w, min_idx, que);
}
return dist[end];
}
private:
vector<int> dist;
vector<bool> checked;
void initialize(const int Vertices)
{
dist.clear();
checked.clear();
dist.resize(Vertices, INF);
checked.resize(Vertices, false);
}
int get_min_edge(priority_queue<Edge> &que) const
{
int min_idx = -1;
while (!que.empty() && checked[min_idx = que.top().idx])
que.pop();
return min_idx;
}
void relax(const Matrix<Edge> &w, const int pivot, priority_queue<Edge> &que)
{
int d;
for (auto &out : w[pivot])
{
if (!checked[out.idx] && (d = dist[pivot] + out.weight) < dist[out.idx])
{
dist[out.idx] = d;
que.push({ out.idx,d });
}
}
}
};
int main(void)
{
int total_cases;
int vertices, edges;
int start, end;
int ans;
Solution s;
Matrix<Edge> w(20000);
int t = 0;
int a, b, v;
cin >> total_cases;
while (t++ < total_cases)
{
cin >> vertices >> edges >> start >> end;
w.clear();
w.resize(vertices);
while (edges--)
{
cin >> a >> b >> v;
w[a].push_back({ b,v });
w[b].push_back({ a,v });
}
ans = s.calculate(w, vertices, start, end);
cout << "Case #" << t << ": ";
if (ans >= INF)
cout << "unreachable" << endl;
else
cout << ans << endl;
}
return 0;
}
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