Legend has it that there was a man named Hu whose father was dying. His father's house has a postal route in the northwest and due west. In order to get there quickly, he took a straight line to the northwest. After he arrived, his father had already left. Before his father left, he always said that it was faster for Hu to ignore online routes than wild roads. Oh, no postal route is faster than this wild road. In order to get to the destination faster, he can choose to take the path. The problem of finding the fastest solution is called the Hu Bugui problem.