# TODO: This exercise is to compute the n-th value of the fibonacci sequence.
#       Fibonacci sequence is a very famous mathematical sequence which can model a lot of nature phenomenon.
#       Details can be found in https://en.wikipedia.org/wiki/Fibonacci_number
#       The fibonacci sequence is defined as follows:
#       1. f0 = 0, f1 = 1
#       2. fn = f_{n-1} + f_{n-2}
#       Take the value of n from the user input. Compute the value of fn.
