"Input Copier" by RamiZk is about 6 months ago and he didn't update it . So I decided to write new one with the ability to edit it to suit you!
Any suggestions is very appreciated. If you found a bug please tell me so I can fix it as soon as I can.
How to use it:
Just click on input or output:
It will turn into red when you click it and it will return white after a second.
Tampermonkey or Violentmonkey or any other open source userscript manager is required. The source is available in Greasy Fork: Input Copier
Tampermonkey extension: Tampermonkey
UPD 1.1.0 : Fixed a bug when you can't copy multiple lines (remember to update it to fix the bug).
UPD 1.2.0 : You can copy output too
UPD 1.2.1 : Fixed firefox bug And Added support for the russian site
UPD: Thanks MikeMirzayanov for destroying the script by adding copy button.
UPD: As I do not have something to do after codeforces copy button update I made Sublime Text Plugin. Check it if you are sublime text user like me!