stuck, 133 bytes

Result

WA

Duration

502ms

Code [DL]

"s=open(0).read().split()
a,b,c,d,e,f,g,h,i=[int(s[i+3])-int(s[i%3])for i in range(9)]
print(a*(e*i-h*f)+b*(f*g-i*d)+c*(d*h-g*e))/6"~

stdin

83 18 87
55 17 40
49 95 95
29 87 03

stdout

stderr

Traceback (most recent call last):
  File "stuck.py", line 167, in <module>
    main()
  File "stuck.py", line 162, in main
    process(prog, stack=[], t=0, nest=0)
  File "stuck.py", line 55, in process
    stack = plugins[plugin].CMDS[char](stack)
  File "plugins/stuck_base.py", line 18, in evl_
    def evl_(s): return s + [eval(s.pop())]
  File "<string>", line 1
    s=open(0).read().split()
     ^
SyntaxError: invalid syntax

strace