Printing ":-)" $$$10^6$$$ times takes about 2.6s in CF (131141089) while it takes just 0.7s in my machine (with 2.4 GHz cpu). I found this issue after tying to solve a problem which required $$$10^6$$$ output lines. My initial blog:

Please take a look at: 4021643 and 6576225. They are exactly same but one runs in 2s the other in 0.1s. Accepted solution was sent 10 month later. Again I submitted same solution after 8 years and got TLE 130976507 while in my computer, runs in just 0.188s

There is a bug in CF compiler for sure, Please solve this issue Mikemizayanov.

Thanks :)

UPDATE: I submitted printing $$$10^6$$$ times program on AtCoder (Link). Here is the result:

Codeforces: 2.6s VS Atcoder: 0.066s