node, 154 bytes

Result

AC

Duration

579ms

Code [DL]

let[,,,a,b,c,d,e,f,g,h,i]=(""+require("fs").readFileSync(0)).split(/\s/).map((e,i,x)=>(e|0)-x[i%3]);
console.log((a*e*i+b*f*g+c*d*h-a*f*h-b*d*i-c*e*g)/6)

stdin

69 07 89
29 51 97
20 93 01
36 14 87

stdout

20944

stderr

strace