I have the cheapest Philips shaver. It is pretty mid. It came with its own charger. On the shaver’s side it looks like a standard ungrounded 220V female connection. But it actually is some propriety DC thingy. Very annoying. Why not just use USB-C?
For integers it really doesn’t exist. An algorithm for multiplying an integer with -1 is: Invert all bits and add 1 to the right-most bit. You can do that for 0 of course, it won’t hurt.
I do have 2 monitors. But I have an opaque side panel. Case closed. Pun intended.