[from
here]
Aidou paused for the second time that night, listening half-heartedly to the radio announcement. The volume was painfully low, so that it didn't attract any unwanted attention. None of it interested him, even as the riddles came easily enough. None of it was useful to him. So far nothing the monkey on the radio had offered had caught his eye, and he doubted that would change.
Stepping into the stairwell, he glanced to the floor. He was willing to bet the other three stairwells on this floor were the same - no stairs leading to the basement, and no stairs leading past the second floor.
So where were the access points? It was a good question.