csharp, 275 bytes

Result

WA

Duration

786ms

Code [DL]

using System;class A{static void Main(){char[]c={' ','\n'};int[]a=Console.In.ReadToEnd().Split(c).Remove("").Select(Int32.Parse).ToArray();for(int z=9;z-->0;)a[z]-=a[9+z%3];Console.Write((a[7]*(a[0]*a[5]-a[3]*a[2])+a[6]*(a[4]*a[2]-a[1]*a[5])+a[8]*(a[3]*a[1]-a[0]*a[4]))/6);}}

stdin

02 29 23
91 51 51
07 93 05
43 99 61

stdout

Compilation failed: 1 error(s), 0 warnings

stderr

/tmp/code.cs(1,99): error CS1061: Type `string[]' does not contain a definition for `Remove' and no extension method `Remove' of type `string[]' could be found. Are you missing an assembly reference?
/usr/lib/mono/4.5/mscorlib.dll (Location of the symbol related to previous error)
Cannot open assembly '/tmp/code.exe': No such file or directory.
rm: can't remove '/tmp/code.exe': No such file or directory

strace