It's fine to work on any problem, so long as it generates interesting mathematics along the way - even if you don't solve it at the end of the day.

I grew up in Cambridge in England, and my love of mathematics dates from those early childhood days.

Pure mathematicians just love to try unsolved problems - they love a challenge.

That particular odyssey is now over. My mind is now at rest.

I know it's a rare privilege, but if one can really tackle something in adult life that means that much to you, then it's more rewarding than anything I can imagine.

But the best problem I ever found, I found in my local public library.

Then when I reached college, I realized that many people had thought about the problem during the 18th and 19th centuries and so I studied those methods.