lua, 219 bytes

Result

WA

Duration

499ms

Code [DL]

a={}for k=1,4 do for s in string.gmatch(io.read(), "[^%s]+")do a[#a+1]=s end end
for z=0,8 do a[z+1]-=a[10+z%3]end
print(math.floor(-(a[8]*(a[4]*a[3]-a[1]*a[6])+a[7]*(a[2]*a[6]-a[5]*a[3])+a[9]*(a[1]*a[5]-a[4]*a[2]))/6))

stdin

61 55 81
55 08 86
49 70 25
55 05 11

stdout

stderr

/usr/bin/lua5.3: /volume/CODE:2: syntax error near '-'

strace