Reasons to be here
Obviously reading this you already have found your path to Codeforces & you have your reasons to be here.
Here are mine:
1. 1. 1.
The beginnings
One step experience
One can setup everything manually repeatlingly for eac problem, but there is no time to waste, so Make it a one step experience. In my case using Java it meant, IntelliJ, CHelper + the Competitive Companion for Chrome
look at performance, time and memory