by writing N parsers (“readers”) and M renderers (“writers”), one could support N × M conversions.

https://pandoc.org/twenty-years-of-pandoc.html#:~:text=by%20writing%20N%20parsers%20(%E2%80%9Creaders%E2%80%9D)%20and%20M%20renderers%20(%E2%80%9Cwriters%E2%80%9D)%2C%20one%20could%20support%20N%20%C3%97%20M%20conversions.