Cache: Clarified the argument by number of children

05-cache/cache.tex

@@ -268,7 +268,8 @@ To establish time and I/O complexity, we consider the tree of recursion. Every n
 to a~T or TS problem. It has 3 or~4 children for its sub-problems. At level~$i$ (counted from the
 root, which is at level~0), we have at most $4^i$ nodes with sub-problems of size $N/2^i$.
 Therefore, the height of the tree is $\log N$ and it has $4^{\log N} = N^2$ leaves.
-Since all internal nodes have at least 2~children, there are less internal nodes than leaves.
+Since all internal nodes have least 2~children (in fact, 3 or~4), there are
+less internal nodes than leaves.
 
 In every TS leaf, we swap a~pair of items. In every T~leaf, nothing happens. Internal nodes
 only redistribute work and they do not touch items. So every node takes $\O(1)$ time and the