cin >> n >> e >> source >> sink;
    for (int i = 0; i < e; i++) cin >> A[i] >> B[i] >> C[i];
    for (int i = 1; i <= n; i++) dist[i] = INF;
    dist[source] = 0;
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < e; j++)
        {
            dist[A[j]] = min(dist[A[j]], dist[B[j]] + C[j]);
            dist[B[j]] = min(dist[B[j]], dist[A[j]] + C[j]);
        }
    }
    cout << dist[sink];