Hello CodeForces Community!

I’d like to invite you to the CodeChef August Cook-Off. As usual, the CookOff will be on the second last Sunday of the month.

Joining me on the problem setting panel are:

• Problem Setter: Morphy (Alei Reyes)
• Problem Tester: kingofnumbers ( Hasan Jaddouh)
• Editorialist: PraveenDhinwa (Praveen Dhinwa)
• Russian Translator: CherryTree (Sergey Kulik)
• Mandarin Translator: huzecong (Hu Zecong)
• Vietnamese Translator: VNOI Team
• Contest Admin and Language Verifier: PraveenDhinwa (Praveen Dhinwa)

Especial thanks go to kpw29 for his appreciation of the problem-set before I send it to CodeChef, he have a good taste in programming contests so I'm glad he found the problems interesting.

The contest theme is based on Lewis Carroll's book Alice's Adventures in Wonderland. Problems are not sorted by difficulty, so I highly recommend to read all of them. This is my second time as problem setter, you can see my previous round at CF328.

I hope you will enjoy solving the problem set. Please give your feedbacks in the comments below after the contest. You can find the rest of the details about the contest below.

Time: 21st August 2016 (2130 hrs) to 22nd 2016 (0000 hrs). (Indian Standard Time — +5:30 GMT) — Check your timezone.

Details: https://www.codechef.com/COOK73

Registration: You just need to have a CodeChef handle to participate. For all those, who are interested and do not have a CodeChef handle, are requested to register in order to participate.

Prizes: Top 10 performers in Global and Indian category will get CodeChef laddus, with which the winners can claim cool CodeChef goodies. Know more here: https://www.codechef.com/laddu. (For those who have not yet got their previous winning, please send an email to winners@codechef.com)

Good Luck and Have Fun! Hope to see you participating!!

UPD. My sad story: I wake up very early to take part on AtCoder, and then to moderate the CodeChef contest, but just before the start of AtCoder there was a power outage on my city :(. Fortunately the contest admin, translators, and tester were able of handling the contest all by themselves :).

UPD. Congrats to the winners!

ksun48

anta

uwi

Here are some hints and bonus to all problems:

BONUS. What is the minimum number of lines that we have to draw to cut every cell?

BONUS. Solve the problem when Dee can remove only a number of stones multiple of x, and when Dum can remove only a number of stones multiple of y

BONUS. Solve the problem when Dee can remove only a number of stones of the form k·x + r₁, and when Dum can remove only a number of stones of the form k·x + r₂

BONUS. Find the lexicographically smallest solution.

BONUS. Can the problem solved efficiently for a general graph? for a planar graph?