Dear Codeforces community,

It's the time of the year again, we believe it will never be too late to celebrate April Fools!

We're excited to invite you to **TOKI Special Open Contest (TSOC) — April Fools 2020**!

Key details:

- Unrated
- Contest link: TOKI Special Open Contest (TSOC) — April Fools 2020
- Time: April 4th 2020, 19:05 UTC+7
- Style: ICPC-Style, no penalty over wrong submissions.
- Scoring: You get the score assigned to the problem when you fully solve it
- Writers: afaji321, athin, Prabowo, Yoshiyuki, and hocky
- Duration: 2 hours
- Problems: 13 Problems
- Allowed languages: C, C++11, Pascal, Java, Python 3

Please register to the contest, and we hope you will enjoy TSOC — April Fools 2020!

We would like to thank yogahmad77, Prabowo as organizers who worked really hard to prepare the contest, and all the writers as testers.

**UPD**: The contest is over! Congratulations to the top 5:

- zscoder, Solved 11 problems, didn't solve F, First solve E, H, and J!
- i_type_stuff, Solved 9 problems, First solve F and G!
- faustaadp, Solved 8 problems, First solve K (One shot)!
- ayaze, Solved 8 problems, Solves D (One shot)!
- Motarack, Solved 8 Problems, Solves E,F,H,I,J,K, and L (One Shot)!

Honorable Mentions:

- rapel, First AC submission!
- BohdanPastuschak, Made a long queue!

Editorial is available here.

Thank you for participating! See you in the next TROC(s)!

he turned himself into a pickle, funniest sht i've ever seen

Hope that this contest will be a fresh air after doing Codeforces' April Fools Contest!

Participated in TOKI Special Open Contest April Fool contest 2016, 2017, 2018 and it was fun. Looking forward for this contest :D.

Thanks for reminding me. Here's TSOC — April Fools 2018! This contest will be available in English only, the same as 2018's.

I am excited for this after partcicipating in previous April fool contest on 1st april.

Надеюсь, этот конкурс не такой странный, как Codeforces апрельский конкурс дураков, но я уверен, что будет весело

Bump!The contest will start soon!Mfw didn't solve the easiest problem (stupid F) and still won the contest.

UPD: Mfw guessed the right answer for C in the last minute lol.

Btw, how to solve tests 1,4,5,7 for M (I think). I tried looking at the past TOKI Regular rounds but only solved all cases except the ones mentioned hmm.

Also, why is the answer to C

Spoiler88

While we are still compiling the results, you can find the editorial here.

Auto comment: topic has been updated by hocky (previous revision, new revision, compare).My approach to all the problems I solved (note that some of them are obviously not intended):

AAnswer is A+B factorial. Somehow I thought it is double factorial for a long time and thus got stuck on this problem (which also costed me F T_T).

BIn the first announcement, there is a white text giving the answer.

CI actually don't know how to solve this problem. However, some guy submitted $$$94$$$ times before the submission limit got reduced to $$$20$$$. Thus, I guess that the answer should be around $$$94$$$. I tried roughly $$$15$$$ values around $$$94$$$ and found the answer.

Thanks BohdanPastuschak for making the $$$94$$$ submissions :)

DNote that A000040 on OEIS are the primes while A072538 is a modified list of primes. Output that sequence.

EOn the first line, output the names of the N students, in any permutation. On the second line, output the N floors where the students live, in any permutation.

Just do that lol

F: ouch

GTwo-letter codes are country codes and you need to output the phone codes. Note that there are country codes that do not begin with the ones given in the map, so I parsed all of them from some random list online.

HMy thoughts during contest: Solve the problem (while making sure you take care of the corner cases). Note that the last sample is wrong (a hoax).

Actual solution: You don't need to minimize the number of days :face_palm:

IDownload the image, and floodfill (with say Paint) to read the hidden text.

JOutput $$$1 + 1 + 2 + ... + n$$$. See this part of statement.

"In other words, after he pays a to visit a-th city and goes back to the first city, he wants a path that costs him the least."

KActually I just started with one deterministic strategy that beats the first 2 cases, and another that beats the last, and select the first one with $$$\frac{2}{3}$$$ probability and the last one with $$$\frac{1}{3}$$$ probability. It should pass in expected $$$7$$$ tries.

After seeing actual solution: Wow, so it really is random after all lol.

LOutput $$$0$$$. I just saw the sample and YOLOed.

I understood that number of my submissions will be a hint for others:) At first I assumed answer be not more than some reasonable value, but after ~30 submissions it was hard to stop)