Hello Codeforces!
I thought it would be interesting to see what default code different users use during contests. By "default code", I mean some pre-written code that can contain any good functions, classes that can be used during a contest. If you have a usual code to use, feel free to share or explain it.
To start things off, I made a video of the code I use. If you find it useful, feel free to copy it and use it in your next contest :)
I use include for stdc++, define int long long int, namespace std, 2 templates for easily inputting and outputting vectors, and one for easily outputting maps (for debugging), custom_hash, a round up division function, and an isPrime function.