Hello Codeforces,
The following is a C++20 user-defined template class modular arithmetics $$$\mod radix$$$, where $$$radix > 1$$$ is a prime number, and all numbers are normalized to the closed interval of non-negative integers $$$[0,radix-1]$$$.
template<int radix> class mod
The template class can was used successully in 247415519, and can be used as any other shared C++ library template class available in the public domain.