Let's denote the function $f(s)$ that takes a string $s$ consisting of lowercase Latin letters and dots, and returns a string consisting of lowercase Latin letters as follows:

1. let $r$ be an empty string;
2. process the characters of $s$ from left to right. For each character $c$, do the following: if $c$ is a lowercase Latin letter, append $c$ at the end of the string $r$; otherwise, delete the last character from $r$ (if $r$ is empty before deleting the last character — the function crashes);
3. return $r$ as the result of the function.

You are given two strings $s$ and $t$. You have to delete the minimum possible number of characters from $s$ so that $f(s) = t$ (and the function does not crash). Note that you aren't allowed to insert new characters into $s$ or reorder the existing ones.