program kadai
implicit none
integer  ::  n
integer,allocatable  ::  a(:)
integer  :: ue,i
integer  ::  shita
real(8)  ::  ans

read(*,*) n
allocate(a(n))
read(*,*) a

do i=1,n
    ue=ue*a(i)
end do

do i=1,n
    shita=shita+ue/a(i)
end do

ans=real(ue,8)/real(shita,8)
write(*,*) ans

end program kadai