JOINT FILING AGREEMENT OF THE REPORTING PERSONS

EXHIBIT A

JOINT FILING AGREEMENT OF THE REPORTING PERSONS

WHEREAS, in accordance with Rule 13d-1(k)(1) under the Securities and Exchange Act of 1934 (the "Act"), only one joint statement and any amendments thereto need to be filed whenever one or more persons are required to file such a statement or any amendments thereto pursuant to Section 13(d) of the Act with respect to the same securities, provided that said persons agree in writing that such statement or amendments thereto is filed on behalf of each of them:

NOW, THEREFORE, the parties hereto agree as follows:

SailingStone Capital Partners LLC, SailingStone Holdings LLC, MacKenzie X. Xxxxx and Xxxxxxx X. Xxxxxxx Xx., do hereby agree, in accordance with Rule 13d-1(k)(1) under the Act, to file a statement on Schedule 13D relating to their ownership of the Common Stock of the Issuer, and do hereby further agree that said statement on Schedule 13D shall be filed on behalf of each of them.

Dated: February 14, 2019

	SailingStone Capital Partners LLC
	By:	/s/ Xxxxxxxx Xxxxx
	Name:	Xxxxxxxx Xxxxx
	Title:	Chief Compliance Officer
	SailingStone Holdings LLC
	By:	/s/ MacKenzie X. Xxxxx
	Name:	MacKenzie X. Xxxxx
	Title:	Managing Member
	MacKenzie X. Xxxxx
	By:	/s/ MacKenzie X. Xxxxx
	Name:	MacKenzie X. Xxxxx
	Xxxxxxx X. Xxxxxxx Xx.
	By:	/s/ Xxxxxxx X. Xxxxxxx Xx.
	Name:	Xxxxxxx X. Xxxxxxx Xx.