Today I got nerd sniped by the prime minister of Canada. For various reasons, I decided to read his so-called autobiography (presumably ghost written or brilliantly edited): https://www.amazon.com/Common-Ground-Justin-Trudeau-ebook/dp/B00K53WAU0
...which contains a puzzle that I'll summarize as: let's say I go to a corner store and buy four items. What are four prices that when added together make $7.11, and when multiplied together, also make $7.11? (No rounding required.)
This turns out to be a fairly old problem, and trickier than it sounds.
ssh+2FA to all your machines, anywhere, without opening firewall ports.