:import std/Combinator .
:import std/String .
:import std/Math .
solve (find (sum → (eq? (+2020)))) → product
main trim → lines → (map string→number) → (φ (cons ⋔ solve) part1 part2)
part1 [[[~1 : {}0] <$> (drop ^0 1)] <++> (enumerate 0)]
part2 [[[[~2 : (~1 : {}0)] <$> (drop ^0 2)] <++> (enumerate (drop ^0 1))] <++> (enumerate 0)]