Advent of Code

--- Day 12: Leonardo's Monorail ---

   You finally reach the top floor of this building: a garden with a slanted glass ceiling. Looks like there are no more
   stars to be had.

   While sitting on a nearby bench amidst some tiger lilies, you manage to decrypt some of the files you extracted from
   the servers downstairs.

   According to these documents, Easter Bunny HQ isn't just this building - it's a collection of buildings in the nearby
   area. They're all connected by a local monorail, and there's another building not far from here! Unfortunately, being
   night, the monorail is currently not operating.

   You remotely connect to the monorail control systems and discover that the boot sequence expects a password. The
   password-checking logic (your puzzle input) is easy to extract, but the code it uses is strange: it's assembunny code
   designed for the new computer you just assembled. You'll have to execute the code and get the password.

   The assembunny code you've extracted operates on four registers (a, b, c, and d) that start at 0 and can hold any
   integer. However, it seems to make use of only a few instructions:

     • cpy x y copies x (either an integer or the value of a register) into register y.
     • inc x increases the value of register x by one.
     • dec x decreases the value of register x by one.
     • jnz x y jumps to an instruction y away (positive means forward; negative means backward), but only if x is not
       zero.

   The jnz instruction moves relative to itself: an offset of -1 would continue at the previous instruction, while an
   offset of 2 would skip over the next instruction.

   For example:

 cpy 41 a
 inc a
 inc a
 dec a
 jnz a 2
 dec a

   The above code would set register a to 41, increase its value by 2, decrease its value by 1, and then skip the last
   dec a (because a is not zero, so the jnz a 2 skips it), leaving register a at 42. When you move past the last
   instruction, the program halts.

   After executing the assembunny code in your puzzle input, what value is left in register a?

   Your puzzle answer was __________.

--- Part Two ---

   As you head down the fire escape to the monorail, you notice it didn't start; register c needs to be initialized to
   the position of the ignition key.

   If you instead initialize register c to be 1, what value is now left in register a?

   Your puzzle answer was ___________.

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