https://haskellchallenge.com/2026-10-271.0 https://haskellchallenge.com/rules2026-10-270.4 https://haskellchallenge.com/facts2026-10-270.8 https://haskellchallenge.com/partner2026-10-270.3 https://haskellchallenge.com/c/7-day-haskell-exercise2026-10-270.6 https://haskellchallenge.com/c/write-a-tiny-program2026-10-270.6 https://haskellchallenge.com/c/recursion-puzzle2026-10-270.6