[Oops.] Typo in Chapter 1 Problem 16 (weighted median)

[raenye]

Please verify that the error is present in the most recent revision before reporting. Yep.

Chapter number or note title: Chapter 1: Recursion.

Page number: Page 53, line 4, (problem 16).

Error description: "The weighted median of R is any x..."

Suggested fix (if any): replace R by S in the definition.