3. The turtle crawled out of its house and moved in a straight line at a constant speed of 5 m/hour. After an hour, it turned $90^{\circ}$ (right or left) and continued moving, then crawled for another hour, then turned $90^{\circ}$ (right or left) again... and so on. It crawled for 11 hours, turning $90^{\circ}$ at the end of each hour. What is the shortest distance from the house it could have been?
Answer 5 m.

Solution: We can consider a coordinate grid with nodes spaced 5 m apart. It is clear that the turtle crawls along the nodes of this grid. In 11 hours, it cannot return to the initial position. However, it can be 5 m away - it is easy to construct an example.