Think of a way to write addition of four numbers using maximum possible braces?
(+ 1 2 3 4)
(+ (+ 1 2) (+ 3 4))
(+ 1 (+ 2 (+ 3 (4))))
(+ 1 2 (+ 3 4))
Answer and explanation
In this 3 times braces () are used. Other possible way is (+ 1 (+ 2 (+ 3 4))) in which again 3 braces () are used.
