All robots avoid Obstacle 1 and Obstacle 2. Excavator 1 and Dump Truck 1 go to Obstacle 1 to clear it through excavation and unloading, then all robots are allowed to pass through Obstacle 1. Excavator 1 and Dump Truck 1 go to Obstacle 2 to clear it through excavation and unloading, then all robots are allowed to pass through Obstacle 2.