set/p q=
for /f "tokens=1-12 delims=%q:~8,1% " %a in ("%q%") do (
set/ad=d-a
set/ae=e-b
set/af=f-c
set/ag=g-a
set/ah=h-b
set/ai=i-c
set/aj=j-a
set/ak=k-b
set/al=l-c)
set/av=(d*h*l+e*i*j+f*g*k-d*k*i-e*l*g-f*j*h)/6
echo %v%