What is the description of the type of the company who concluded its contracts most recently?
select t1.company_name from third_party_companies as t1 join maintenance_contracts as t2 on t1.company_id = t2.maintenance_contract_company_id join ref_company_types as t3 on t1.company_type_code = t3.company_type_code order by t2.contract_end_date desc limit 1