Fixed a small typo

Author: luc4leone

1-js/06-advanced-functions/01-recursion/article.md

@@ -319,7 +319,7 @@ let company = {
 In other words, a company has departments.
 
 - A department may have an array of staff. For instance, `sales` department has 2 employees: John and Alice.
-- Or a department may split into subdepartments, like `development` has two branches: `sites` and `internals`. Each of them has the own staff.
+- Or a department may split into subdepartments, like `development` has two branches: `sites` and `internals`. Each of them has their own staff.
 - It is also possible that when a subdepartment grows, it divides into subsubdepartments (or teams).
 
     For instance, the `sites` department in the future may be split into teams for `siteA` and `siteB`. And they, potentially, can split even more. That's not on the picture, just something to have in mind.