Vector Product in Fortran

program vectorcalc

implicit none

real(8) a1,a2,a3,b1,b2,b3,c1,c2,c3
real(8), dimension (:), allocatable :: vectorA(:),vectorB(:),vectorCross(:)
integer dim
real(8) :: dot_product


write(*,*)'enter vectorA,B,Cross dimension'
read(*,*) dim
write(*,*)'entered dimension is', dim

allocate( vectorA (dim))
allocate( vectorB (dim))
allocate( vectorCross(dim))

write(*,*)'enter vectorA values'
read(*,*) a1,a2,a3
write(*,*)'enter vectorB values'
read(*,*) b1,b2,b3

vectorA= (/a1,a2,a3/)
vectorB= (/b1,b2,b3/)

if(dim.eq.3) then 

c1=a2*b3-a3*b2
c2=a3*b1-a1*b3
c3=a1*b2-a2*b1

vectorCross=(/c1,c2,c3/)

    write(*,*) 'a x b:', vectorCross

    write(*,*) 'a*b:', dot_product(vectorA,vectorB)
else 
    write(*,*) 'a*b:', dot_product(vectorA,vectorB)
end if


deallocate (vectorA)
deallocate (vectorB)
deallocate (vectorCross)

end program vectorcalc