Hello everyone!

That is Codeforces Round 139 for the second division only. Members of the first division can participate out of competition.

Round is prepared by Ripatti , Gerald , Delinur.

We will use dynamic score system. Problems will be ordered in order of expected increasing difficulty.

Good luck!

**UPD.** For technical reasons round delays in 15 minutes.

**UPD2.** Testing is complete. Winners:

1. wccy

2. ttl

3. shubhanshu

4. Atarashi_Ako

5. Dshawn

2 members solved all 5 problems.

English editorial will be tomorrow. You can try to understand russian editorial.

**UPD3.** English editorial.

and problems score???

Time for the contest is 23:30 in China. It's toooo late

Better than no contest, right?

Missed the registration. Didn't know contest was today. Quite quick back to back to contests.

I wonder what is the solution of E. Anybody write in short please.

brute force + OEIS

what do you mean by OEIS?

http://oeis.org/ You can find many integer sequences there

http://oeis.org/

thank u for the help. Do you mean the solution is that first brute-force some result and then search the sequence on OEIS?

You are searching for

`1, 2, 4, 6, 12, 16`

or other sequence?Not this sequence, Okay, I may misunderstand the method

There are only 39 numbers in OEIS, so I think the problem is

`Unsolvable`

with`N = 40`

and My solution got Wrong answer on test 40 :((.40th Mersenne Prime :/ http://mathworld.wolfram.com/news/2003-12-02/mersenne/

Thank you!

You can you wiki instead. Mersenne_prime And it equals to 2 ^ 20996011 — 1.

Thank you!

I finished Div.2 C problem just 5s late... Bad luck...

"It started like a Cheetah , but now is as slow as a snail "- yes , the system testing

Solutions to A and E of wccy and wzc1995 are ditto same.

So slow.. =/

Although my program of problem C is passed by the system test, my total scores in the scoreboard does NOT add the score of the problem C as well as my new rating. Please recalculate my score and new rating.

For this 139 competition, I receive notification on E-mail 4 hour after contest!

225D - Snake In the problem was said that the snake's head is "1", the second segment is "2", and so on to k. But in the sixth test the snake starts from 5 to 9. Where is the first part from 1 to 4?

I saw it — http://codeforces.ru/blog/entry/5322#comment-105121

Because some large test case may be not display completely

I'm having some troubles generating the K-bonacci numbers on problem B. I tried to just implement the recurrences describe in the problem statement, but I suppose I have a bug somewhere. Can anyone help? Thanks.

`while(n > K)`

is wrong. You should add every F(x) for x in [n — K — 1, n — 1].Thank you for the help. I changed the loop to be like this, but I never get 3 as one of the K-bonacci numbers when using K=2. However, according to example 1, 3 is supposed to be one of the numbers.

At any rate, I don't want to waste anyone's time here, so I will try to study some other solutions to see if I can use them as a reference. Thanks very much again for your help, I really appreciate it.

Can anyone tell me what is the relation between Mersenne primes and the answer of Problem E???? I mean what is the proof that (2^(Mp-1)-1) don't have an answer to the equation??? I will appreciate a proof or a reference to be read! ;)