Script/Plugin for bulk import categories into Wordpress

I am migrating my website from another CMS to WP. I have a csv file with more than 10,000 rows with 6 columns - continent, continent_id, country, country_id, city, city_id. I wish to import these as nested categories in WordPress with the category name as slugs. There will be 3 levels (continent -> country -> city) I need a solution which would help me do this efficiently - it can either be a plugin or a php script that I run once to import the data. The challenges are: 1) Some city and country names are the same (e.g., country-> Hong Kong, city-> Hong Kong). WordPress does not allow duplicate slugs. In this case it is OK to add a 2 behind the duplicate (i.e., city) slug to differentiate it from the country slug 2) I want the continent, country and city IDs to be preserved in the WP database as as I need to bulk import posts into WP later using the IDs as identifiers linking the posts to their respective categories. The IDs for continent, country and city IDs are unique only within the same column (i.e., there can be a continent with ID=2 and also a country with ID=2, but there will not be 2 continents with the same ID). And these IDs should not be changed from their original. If I am not wrong a custom taxonomy would solve it, but I'm not too advanced at WP and not sure how to build a solution myself. If you are able to propose a solution using custom taxonomy please do suggest. When you bid for this project, please specify: 1) Your recommended solution (don't just tell me that you have worked on many Wordpress jobs before and you can do it - I need to know what your solution is so that I can tell if it will work) 2) How many hours you will need for this. It's not a difficult task, just need some custom scripting, so I am looking for someone who is confident of doing it fast.