Is it a good idea to keep solving only HARD problems leaving aside the medium ones. Right now I am able to solve HARD problems, but they are consuming a lot of time - sometimes I need 2 or 3 days to solve a single problem and in general at least 2 or 3 hours! Because of this, I am unable to practise much or my practise feels diffused, so should I continue doing this hoping to get faster at solving the hard ones or should I keep solving medium ones too - may be 70% medium questions and 30% hard ones should do fine right?

Also, I would be happy to hear what you would have done!

Thanks for the advice!