Three people, one road.
Road builders have formed a network of many roads, and the road signs are always cold and straight. Travelers carrying heavy luggage can only follow the road signs step by step and walk along the path in an unknown direction. Aishayou was always smart enough, so the traveler drew his own marks on the road signs and walked on the newly opened path before the road builders.
One road, twenty years, three people, four fields, only one red thread, how to tie it?