I am taking combinatorics, now...
I remember I was doing pretty well when I took in during undergrad years, and it was like three years ago from now.
Before I say something, I should must note that combinatorics is usually told as young men's mathematics for majority of people...
And now, I really feel that big difference in three years.
It's also probably because I never solved so much problems regarding combinatorics recently, and my concentration was highly on algebra, but still...
It should be a common sense problem, but I lose my focus...
Sigh... I guess I got old too quickly...
