Welcome dear friends)

We are glad to introduce you regular Codeforces round #113 for Div.2 participants. Everyone can traditionally participate in it.

Problems are prepared by known command of authors: Kholkin Pavel (HolkinPV), Nikolay Kuznetsov (NALP), Artem Rakhov (RAD). Also thanks to Gerald Agapov (Gerald) for his help, Michael Mirzayanov (MikeMirzayanov) for Codeforces system and Mary Belova (Delinur) for translating problems.

**In todays contest would be one innovation. Score distribution would be dynamic. More information you can find here)**

We hope that todays round would be succesful. We wish you good luck and high rating!

**UPD**: The contest is over. Hope you enjoy the problems) the editorial is already here)

Congratulations to winners:

My friend tried to register and got the message "Cannot register user now. Try later or contact the administration.". Why?

And I have registered twice.

help him~~~~~~

That wasn't a good idea . At least If you told before I think that would be better . But thank you for your great idea . Hope best for everyone .

Can anyone give some hint(s) for problem D? :D

A typical DP problem, but you must record the <shoeId, customerId> pair during the dp loop.

If after the test completed, the number of contestant who can solved the problem change, will it change the problem's score?

Yes, the problems' score can change after system testing.

On the Contest page, both of 114 CF contest are for DIV 1 ?

I was wondering what point distribution the author had thought for the problem set ?

Any tutorials coming?

There is Russian one

Please publish the editorial in English, is the second consecutive round that comes only in Russian. If not possible, some better than the google translator.

http://codeforces.com/blog/entry/4173?locale=en

Please provide the Editorial in English..otherwise wont get any benefit by mere participation !!

It's already published. http://codeforces.com/blog/entry/4173?locale=en

Thanks !! Please explain the approach to Problem E ie Tetrahedron.

Okay, the solution is DP. Let's number the vertices A, B, C, D from 0 to 3 instead, and let dp[i] mean how many cyclic paths currently begin and end at i. At first, we only have dp[3] = 1 and dp[0] = dp[1] = dp[2] = 0, and we only are considering paths of length 1. Now, to calculate how many cyclic paths of length n there are, you iterate n times, updating the DP table in the following manner (pseudocode): http://pastebin.com/XyNsyMk6

help!help!I got a WA on test #12,my code is [submission:1403496]，the former 11 tests are all passed, Who can help me find out the problem of my code?

You shouldn't

`/4`

because 3^n is modular (try`*(1000000008/4)`

)Thank you for your help! :)

In order to divide on 4 by modulo of 1e9+7 you need to multiply by its inverse (found with extended gcd or basing on Fermat's theorem).

:)thanks a lot!