Euler – Coder.si

Yarra Gnisrever

Problem 680

Let and be two positive integers.

is the -th Fibonacci number: , for all .
Let and let .

Start with an array of integers where initially every is equal to .Now perform successive operations on , where the -th operation consists of reversing the order of those elements in with indices between and (both ends inclusive).

Define to be after operations.

For example, , as can be seen from the following procedure:

Initial position:
Step 1 - Reverse to :
Step 2 - Reverse to :
Step 3 - Reverse to :
Step 4 - Reverse to :

Also, and .

Find giving your answer modulo .