rprogn, 294 bytes

Result

WA

Duration

508ms

Code [DL]

read"%d+" ↔ pop "l" = pop "k" = pop "j" = [
read"%d+" ↔ pop l - "c" = pop k - "b" = pop j - "a" = [
read"%d+" ↔ pop l - "f" = pop k - "e" = pop j - "d" = [
read"%d+" ↔ pop l - "i" = pop k - "h" = pop j - "g" = [
a e i * * b f g * * c d h * * + + a h f * * b i d * * c g e * * + + - 6 //

stdin

81 81 33
56 08 06
77 20 48
42 29 35

stdout

--------------------
MEMORY DUMP
--------------------
--------------------

stderr

/usr/bin/lua5.3: main.lua:1330: ERROR: "main.lua:938: attempt to index a nil value (local 'a')" AT WORD 3, '↔'
stack traceback:
	[C]: in function 'error'
	main.lua:1330: in local 'stuff'
	main.lua:1356: in function 'rpn'
	main.lua:1374: in main chunk
	[C]: in ?

strace