You are in position (0, 0) of a coordinate plane. You want to determine if you can reach point (x, y). There are n different types of steps that you can make. Step type i is represented by two non-negative integers a_i, b_i which means that a step of type i moves you a_i steps to the right and b_i steps up.

How to determine if it is possible to reach point (x, y) using only those type of steps? You are allowed to use a type of step multiple times but you can't do half of a step.

Can this problem be solved with time complexity better than O(x * y * n)?

I think that what happened in Round 382 is just a reflection of the real problem with Codeforces: it takes 1 year so that your problems become a contest (the problem setter said he waited for a very long time and meanwhile he uploaded his problem to SPOJ). I know making a contest is a complicated process, but there is a lot of room for improvement in this area. It should take less time to make a contest, and this will result in more frequent contests :)

Now that I got your attention... (no, codeforces didn't force me to do anything) but for real, why almost none of the contests are on weekends? I can only compete in contests during the weekend due to school/job,, so my involvement in competitive programming has been reduced drastically (cause I only do Codeforces because it's the best!). This has always been an issue, but I believe recently it has been worse than ever. Are there other people in a similar situation as me?

UPDATE AUG 6: We did it guys! Tomorrow's contest is in a Sunday =O

I like it better because I get 5 more minutes to make it to the round,, but what is the official reason?

Frequently I have been asked by non-CS people what do I do in a competitive programming contest, but I never feel satisfied with my response. How would you answer?

Any opinions? Just wondering...

IOI 2014 is in about a week and there is still no IOI 14 facebook group, so I have created one. Invite other IOI 2014 participants!

https://www.facebook.com/groups/1506154232931553/

What do you prefer: to know your and everyone's else results right after you finish the exam (IOI), or to know your scores few days after the exam and only know partially the ones of the other contestants (IMO)?

Who answers clarifications during Codeforces contests? Problem setters? And about how many questions in average are there per contest? I imagine that usually very few, but when there is a small mistake on the statement, tons of simultaneous questions would arrive haha. I was just curious :)

It would be nice to also include stats about questions on each contest, like how many questions there were, and show the most funny ones.

The majority of Codeforces contests take place from Monday to Friday; however, many users of Codeforces are students who are in class during those contests, and are unable to participate. :(

Why are there so many contests in those days, and just few in the weekends?

Which problem was your favorite of 2013?

Motivating problem: You have an array of size N with N different numbers; calculate the sum of the numbers in the interval of a to b.

What is the proof that a Segment Tree performs those queries in log(n) time? Or where can I find the proof? Thanks.

I have seen people that enter to a contest in Codeforces and they just see the problems, try to solve them but can't. Happily those people didn't submit anything so their rating remains untouched; however, some people that actually could solve one problem get penalized in their rating much more than the ones that couldn't solve anything but didn't submit.

In my opinion, if you are registered for a contest and you enter to it at the time of the contest, it should count towards your rating regardless if you submitted something or not.

What do you think?

Which year's IOI has been your favorite one and why? I'm just curious :P

Hi,

If you are located at the bottom left corner (0, 0) of a plain with H x W cells, and you move U positions up and R positions right in each step, how to calculate if you will eventually arrive to a specific cell after any amount of steps? (If you fall to the right of the plane, you get to the left of the plane. Same with falling up)

Thanks.

It's just a curiosity question

:P

I have heard some opinions but I still can't decide. What do you think?

Hello,

I found this Div 2 — A problem quite interesting. The tutorial gives a quadratic solution; however, I was wondering if there was a linear solution. Any ideas? Just for the fun.

Thanks.