P1: Construction was tricky. Fortunately the second part was straightforward. Took me maybe 45 distracted minutes?, after which I thought the construction seemed familiar and I realized I had seen the problem before in a 2011 handout. Oops.

(And then some moderator — I still don't know who — deleted the post where I pointed this out along with a bunch of others, as well as locking a lot of meta-discussion threads, and some mild forum drama ensued.)

(Usually when this happens mavropnevma finds a convincing source and shows up to chew out the PSC )

P6: Nice and intuitively interesting statement, and I took a long time to solve it (maybe because I was too lazy to use any scratch paper and made the final breakthroughs while lying in bed sleepless at 1 AM), but I thought it was kind of disappointing when I realized the final step was just a pretty routine-looking counting/summing-in-two-ways. Meh.

P2,3,4,5: Life's too short for anything that's not combinatorics~~~

(ok, I heard 2 is bashy and has too many solutions like 2012.4 from my year and I think I have something like the bound that gets rid of all but finitely many cases so I'm kind of satisfied; I think I've been spoiled on the most important step for 3 because it's everywhere; easy geo 4 looks boring. Who knows, I might try 5 later.)

(Taiwan teammates predict what looks like mostly silvers. Although since most of them are new this year I think that's not bad.)

(Today is a flat parentheses layout day, it seems.)