Layered Network Flow

**Bài toán.** Line 1: n m s t; then m lines u v c. Print the maximum flow from s to t. **Constraints:** 1 ≤ n, m ≤ 100 000; 1 ≤ c ≤ 10^9. Dinic required: BFS level graph + DFS blocking flow. Unit-push augmentation times out on the layered load.