Answer the following question based on the information given below.
For a real number x, let
f(x) = 1/(1 + x), if x is non-negative
= 1+ x, if x is negative
f n(x) = f(f n – 1(x)), n = 2, 3, ....
r is an integer > 2. Then, what is the value of f r – 1(–r) + f r(–r)+ f r + 1 (–r)?