Welcome to Codeforces Beta Round #72.

The authors of the round are: Kholkin Pavel, Nikolay Kuznetsov and Kaluzhin Alexander. This round is for both divisions. You will get different problems and we hope that every participant solve as much problems as he can.

Thanks to Rakhov Artyom and Pavel Kuznetsov for their help, Mary Belova for translating problems and Mike Mirzayanov for the perfect system.

The main hero of the problems is Valera. Today you should help him in everything. =)

Good luck and high rating for everyone =)

**Upd: the contest is over, congratulations to winners:**

**in div1 -**tourist

**in div2 -**StelZ40494

Where can I see the changes of my rating in a picture?

Please help me. :)

May I know how do I access the full testcase for testcase 56 problem C? The testcase got cut off halfway :S

Ugh, if I swap the order of 2 of my lines of code, I would have gotten AC for what qn :S

Rating graphs disappeared?!They are back now.

The smaller participant the more rating?

May be because the Yandex contest was a mix of div 1 and div 2 contestants but this is a pure div 1.Problem Analysiswill be ready ?May I know how should problem D be done? Here are some ideas I have.

1. K must be prime. If not, the number will have some divisor smaller than K.

2. Suppose K >= 10000. Then, suppose X is a valid number. Then X/K <= 2*10^5. We can check the factors of each X/K up to min(K,sqrt(X/K)). Then the complexity is thus on the order of 10^7.

3. Suppose K <= 10000. I was thinking of applying PIE, but I am not sure how to compute that in a fast manner. :S

Thanks in advance for your help!

System Testing is too slow. I coded for 2 hours and waited to see the result for another 2 hours. Hope the performance of the system can be improved.important for him. Since the doctor works long hours and she can't get distracted like that after all, she asked you to figure it out.

Russian ones:

http://codeforces.ru/blog/entry/1961

http://codeforces.ru/blog/entry/1976

http://codeforces.ru/blog/entry/1979

Thanks for the links. However, do you know when will the English analysis be ready?

Hi All,

Problem — Toy Army (Div 2A)

After solving the problem by hand for n = 2, 4, 6, and 8, I figured the best solution to is

3 * n / 2-. However, I couldn't figure the correctness of the solution, or I don't know why the solution (selecting n/2 soldiers each time) works.From what I know -

Round 1 — Valera can choose any number of soldiers to kill from 1 to n.

Round 2 — Arcady can choose any number of soldiers to kill from (n — killed in Round 1) to n.

Round 3 — Valera can choose any number of soldiers to kill depending on the value selected in the previous rounds.