Best problems — $$$\Theta(thinking)$$$, $$$\Theta(thinking+log(writing))$$$, $$$\Theta(thinking+log(knowledge))$$$, $$$\Theta(thinking+log(knowledge)+log(writing))$$$

Good problems — $$$\Theta(thinking+writing+log(knowledge))$$$, $$$\Theta(thinking+reading+log(knowledge))$$$, $$$\Theta(thinking+reading+writing+log(knowledge))$$$

Nice problems — $$$\Theta(thinking+knowledge)$$$, $$$\Theta(thinking+knowledge+writing)$$$,$$$\Theta(thinking+knowledge+writing+reading)$$$

Mediocre problems — $$$\Theta(thinking+reading)$$$, $$$\Theta(knowledge+writing)$$$

Bad problems — $$$\Theta(reading+writing)$$$, $$$\Theta(reading+log(writing))$$$, $$$\Theta(knowledge)$$$

Hell — $$$\Theta(reading)$$$