leo, 
I've completed "Step Counter" - Day 21 - Advent of Code 2023 #AdventOfCode https://adventofcode.com/2023/day/21
Oh polynomials - I dimly remember you from high school. This problem required me to reinvent calculus. Look for Leo's Principia coming soon.
https://github.com/leolaporte/aoc-cl/blob/main/2023/Day_21/Day_21.lisp