kotlin, 231 bytes

Result

WA

Duration

5070ms

Code [DL]

fun main(args:Array<String>){
val a=(0..3).flatMap{_->readLine()!!+" "}.split(" ").map{a->a.toInt()
for(z in 8 downTo 0)a[z]-=a[9+z%3]
println(-(a[7]*(a[3]*a[2]-a[0]*a[5])+a[6]*(a[1]*a[5]-a[4]*a[2])+a[8]*(a[0]*a[4]-a[3]*a[1]))/6)
}

stdin

61 93 78
77 43 26
52 51 87
03 20 16

stdout

stderr

/tmp/code.kt:5:2: error: expecting '}'
}
 ^
/tmp/code.kt:2:14: error: type inference failed: inline fun <T, R> Iterable<T>.flatMap(transform: (T) -> Iterable<R>): List<R>
cannot be applied to
receiver: IntRange  arguments: ((Int) -> String)

val a=(0..3).flatMap{_->readLine()!!+" "}.split(" ").map{a->a.toInt()
             ^
/tmp/code.kt:2:21: error: type mismatch: inferred type is (Int) -> String but (Int) -> Iterable<???> was expected
val a=(0..3).flatMap{_->readLine()!!+" "}.split(" ").map{a->a.toInt()
                    ^
/tmp/code.kt:2:58: error: cannot infer a type for this parameter. Please specify it explicitly.
val a=(0..3).flatMap{_->readLine()!!+" "}.split(" ").map{a->a.toInt()
                                                         ^
/tmp/code.kt:3:25: error: assignment operators ambiguity: 
public open fun <ERROR FUNCTION>(): [ERROR : <ERROR FUNCTION RETURN TYPE>] defined in root package
public open fun <ERROR FUNCTION>(): [ERROR : <ERROR FUNCTION RETURN TYPE>] defined in root package
for(z in 8 downTo 0)a[z]-=a[9+z%3]
                        ^
Error: Unable to access jarfile code.jar
rm: can't remove '/tmp/code.jar': No such file or directory

strace