another interesting fact: if you have to compute the fib of very large numbers mod n. you can use the fact that the fibonnaci numbers would repeat.( see: https

another interesting fact: if you have to compute the fib of very large numbers mod n. you can use the fact that the fibonnaci numbers would repeat.( see: https://en.wikipedia.org/wiki/Pisano_period https://en.wikipedia.org/wiki/Pisano_period) <spoiler> this allows you to solve problems like this: https://www.spoj.com/problems/FIBHARD/ https://www.spoj.com/problems/FIBHARD/ <\spoiler>