Thank you for the answer. I've got another problem. It seems to be obvious but I can't write the proof. Here is the statement:

If $A$ is a Dedekind domain contained in $k$ field, and $a\in A$, then for a prime ideal $I$ of $A$, if the localization of $A$ at $I$ gives a place(or prime) of $k$ with maximal ideal $P$ , we have $v_P (a) = m$, where $m$ is the power of $I$ in the decomposition of $(a)$ as factor of prime ideals of the Dedekind domain $A$.