* Pyupgrade to Python 3.9 * updating DIRECTORY.md Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
* Add solution to problem 81 - project euler * Update project_euler/problem_081/sol1.py Co-authored-by: Christian Clauss <cclauss@me.com> * Update project_euler/problem_081/sol1.py Co-authored-by: Christian Clauss <cclauss@me.com> Co-authored-by: Christian Clauss <cclauss@me.com>