Recently I've read about rotating calipers technique from wikipedia.But I'm not satisfied with it.I wonder if there is any articles or blogs from where I can learn more about rotating calipers.If you guys have any valuable resources on this topic please share. It'll be great if someone writes a blog about this topic at codeforces.

Is it possible to reach 1900+ from gray within a year?I'm going to pause my academic study for 1 year so that I can give full concentration in coding.I also want to enrich my knowledge as like as WF . I don't have coach.And I don't know what should I do to reach my goal.Can any one tell me it is possible or not?If "Yes" then what should I do to reach my goal?Can anyone suggest me??

http://mirror.codeforces.com/contest/977/submission/38702974 why this solution is taken more time and less memory then

http://mirror.codeforces.com/contest/977/submission/38702053

this solution??

Problem link Here

For last 6-8 month I am doing problem solve in Codeforce. But still I can't solve B problem in contest smoothly.I saw many problem solver who started coding with me and now they can solve C problem even D problem easily.They can think problem easily but that problem i need to think with long time even 1 or 2 week.I feel frustrated when i see them.Now my ques is,what should I do for improve?I want to be a very good problem solver.I know it's all about solve more and more problem.With solving problem,do i need to do anything?

Is there any way to find prime number upto 10^9 or more in 1 second?