# Length of the orbit (semiclassical orbits)

$$d(E)=d_{0} (E)+ \sum_{p.o}A_{p}Cos(S(E)\ell_{p})$$
and $\ell_{p}$ are the length of the orbit.
However my question is, how can one derive the length of the orbit from the potential inside the quantum Hamiltonian. $$H=p^{2}+V(x)$$.