by@yamayu832
WA
494ms
<?=[$a,$b,$c,$d,$e,$f,$g,$h,$i,$j,$k,$l]=explode(" ",readline()." ".readline()." ".readline()." ".readline()),$g-=$a,$h-=$b,$i-=$c,$j-=$a,$k-=$b,$l-=$c,(($e-$b)*($i*$j-$g*$l)+($f-$c)*($g*$k-$h*$j)+($d-$a)*($h*$l-$i*$k))/6;
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Array2167-723851-499552
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