There are many simple problems, which require a few elementary calculations for solving them. But some solutions get AC in 0.015 and some only in 0.031, although they do almost the same things. And it's interesting for me what is the main difference between such programs?

Some time ago I wanted to ask this question about 0.001 and 0.015 solutions, but now I just don't see any programms getting AC in 0.001. What has happened? There are no 0.001 solutions for the latest contest's problems!

I can't say that it is very important for me, but it's just interesting to know the answer))