I’ll just place this here:

You have to compute this expression.

This riddle was composed a few months ago for a competition, but we decided to not use it in the end. Actually, it is easier than it seems: You don’t need any calculator or computer to solve it. A piece of paper (or two) should be enough. We wrote the riddle in a way that there are several shortcuts that can be used to solve it, but if you don’t find the shortcuts, you can still solve it in the obvious way, taking just a little bit longer.

Also, you have to find the exact answer, not a numerical approximation.

I’m not posting the answer here for now. If you’re curious whether your answer is correct, post below.