I have an interesting problem for you. 
Well, this is a problem from Gordian Knot '15. And, I shall be bold enough to assume that it succeeded in engrossing you :)
Felicity Threads of IIIT Hyderabad would like to invite you to participate in Gordian Knot, a Project Euler style mathematical contest. For the real world counterparts of Charlie Eppes, of Numb3rs, this contest promises to be an enthralling experience especially if your forte is the field of mathematics and computing.
Contest Start: 0130 HRS IST (UTC +0530 HRS), January 10 2016
Contest End: 0130 HRS IST (UTC +0530 HRS), January 11 2016
Click here to go to the contest
Follow live updates! :D
Prizes worth INR 15k to be won!
And, if that isn't enough, there's always bragging rights! ;)
Just have a look at last year's final standings :) 
P.S. The answer is 999999999996
Auto comment: topic has been updated by tanmaysahay94 (previous revision, new revision, compare).
I guess the above problem is straight forward Carmichael's Theorem ?
Trying to untie the knot so quickly? ;)
How to get it?
Don't tell me that the problem has got you all knotted up :P
Auto comment: topic has been updated by tanmaysahay94 (previous revision, new revision, compare).
С нетерпением жду этого.
Нетерпением ждем этого, tanmaysahay94!
Can't wait for this!
:D
Well, will have to wait for 90 more minutes :(
Auto comment: topic has been updated by tanmaysahay94 (previous revision, new revision, compare).
Auto comment: topic has been updated by tanmaysahay94 (previous revision, new revision, compare).
Auto comment: topic has been updated by tanmaysahay94 (previous revision, new revision, compare).
As a part of the team which organized this contest last year, which included me, karanaggarwal, primate, and darkshadows, I am sure that the contest this year also will be of high quality. Good luck to everyone for it. Let's see how it goes this time. :)
:)
Unfortunately, we had some technical difficulties, so we're postponing the contest by 90 minutes. We'll be posting the registration link in a few minutes, please register then. Sincere apologies for the delay.
Contest going live soon!
Register at https://felicity.iiit.ac.in/auth/
"soon" -_-
Any update on when the contest is going to start?
Seems like in another hour. They had silently updated the start time on the website.
Still not on.. wasted 2 hours for this
A humble suggestion, I think its better to atleast release the problem statements of 1st level as pdfs or something so that people will be occupied with solving problems
Event cancelled ! This was the least I expected :\
EDIT : Thanks for further clarification!
Sympathies with the problem setters
With great regret, we announce the postponement of Gordian Knot. We are aware that a number of people were eagerly awaiting the contest and we know that we let them down. We sincerely apologize.
This year we tried to restructure the portal using the Django REST API, that could not be tested properly in due time. Despite our repeated efforts to get things up and running, we were unable to deploy the contest portal due to issues faced in integrating a django-cas library with our Django backend server. Lack of planning and scheduling on our part is palpable and unacceptable. We assure you that we are putting in our best for the rest of Threads.
Consequently, there has been a change in the schedule for Threads ʼ16. Gordian Knot has been postponed to January 17, 0000 hours IST.
Even though one thread has crashed, the process still lives. Let’s not make it a daemon. We look forward to your participation because you make Threads what it is.
With all humility, we can host such high-impact contests on HackerEarth. The platform has become very robust now after hosting hundreds of contests. Moreover, it's advisable to setup a mirror contest on another platform especially when it is on a new development platform. Let me know if I can be of help in anyway.
P.S. I am CTO of HackerEarth and I know how it feels to run into such issues. Just want to offer my 2 cents here.
As informed earlier, the contest starts at 0000 hours on 17th Janurary 2016.
Link to the contest: https://felicity.iiit.ac.in/threads/gordian-knot/
Register yourselves at https://felicity.iiit.ac.in/register/
To follow live updates, visit our Facebook event page at https://www.facebook.com/events/1655403074711981/
In problem 7.1 what is wrong in solution:
First part is number of divisors of 2004 except 1 and 2004, so k=14
Second part calculate by dynamic on submasks, so r=381024000
Third part there are two linear functions f(x) = 5184*x and f(x) = -5185x, so answer is 381024000*(5184+5185) = 3950837856000
For the first part I got the number of even divisors of 2004, so that gave me k=8 The second part was easily calculated as r=5184. Third part the linear functions are 5184r and -5185r so answer was 5184*(5184+5185)=53752896. This got accepted.
Got it
When and where the editorial is going to be published? I liked most of the porblems, but I hated that level 6 had just 3 problems(instead of 5) so solving 2 of them I couldn't advance to level 7. Anyway congrats for contest. And, since the editorial is not published yet, can somebody tell me how he solved 6.2? it's prerty interesting(I tried C (number of points, 3) — number of ways to get 3 coliniar points put I wasn't able to compute this number)