Which country has decided to withdraw its membership from OPEC as of January 2019?

Qatar country has decided to withdraw its membership from OPEC as of January 2019. The OPEC is The Organization of the Petroleum Exporting Countries founded in Baghdad, Iraq, with the signing of an agreement in September 1960 by five countries namely Islamic Republic of Iran, Iraq, Kuwait, Saudi Arabia and Venezuela. They were to become the Founder Members of the Organization.