Question 173
On a $5 \times 5$ board, a chess game rider is in the house marked with $A$. Then he moves marking the houses where he passes: $A \rightarrow B \rightarrow C \rightarrow D \rightarrow E \rightarrow F \rightarrow G \rightarrow H$.
| $A$ | | | | $G$ |
| :--- | :--- | :--- | :--- | :--- |
| | | $H$ | | |
| | $B$ | | $F$ | |
| | | $D$ | | |
| $C$ | | | | $E$ |
Starting from the house $H$, the rider moves through the board until he has passed through all 25 houses. Describe the route he took.
| $A$ | | | | $G$ |
| :--- | :--- | :--- | :--- | :--- |
| | | $H$ | | |
| | $B$ | | $F$ | |
| | | $D$ | | |
| $C$ | | | | $E$ |
Starting from the house $H$, the rider moves through the board until he has passed through all 25 houses. Describe the route he took.