I think I understand it by looking at bitcoin.stackexchange.com/a/2926/139641. If I understood it correctly, because the first digit of the target I calculated is higher than 0x7f, I should prepend a zero digit and then the compact form would be 1d00d86a

Thank you for the answer. Okay, so I understand that 1cd86a52 is invalid because it represents a negative number, but then how do I get to 1d00d86a?

Thank you for this answer! Yeah, I got the idea of the text, I imagined it was just omitting the fact that each party still needs to know about the other parties' inputs. Just wanted to make sure I wasn't missing anything