4. The robot moves along straight segments, making turns of 90 degrees to the right or left every minute (neglect the time for turning). The robot travels 10 meters per minute. What is the minimum distance from the starting position the robot can be after 9 minutes, if it did not turn during the first minute?
Answer: $10 \mathrm{~m}$

Solution: We can consider a coordinate grid with nodes spaced 10m apart. Clearly, the robot moves along the nodes of this grid. It cannot return to the initial position in 9 minutes. However, it can be at a distance of 10 m - it is easy to construct an example.