Exhibit A

JOINT FILING AGREEMENT

PURSUANT TO RULE 13D-1(K)(1)

The undersigned acknowledge and agree that the Statement on Schedule 13D filed with the Securities and Exchange Commission on or about the date hereof with respect to the beneficial ownership by the undersigned of the shares of Class A Common Stock, par value $0.0001 per share, of Churchill Capital Corp. III is filed on behalf of each of the undersigned and that all subsequent amendments to this statement on Schedule 13D shall be filed on behalf of each of the undersigned that is named as a reporting person in such filing without the necessity of filing an additional joint filing agreement. The undersigned acknowledge that each shall be responsible for the timely filing of such amendments, and for the completeness and accuracy of the information concerning it contained therein, but shall not be responsible for the completeness and accuracy of the information concerning the others, except to the extent that it knows or has reason to believe that such information is inaccurate. This joint filing agreement may be executed in any number of counterparts and all of such counterparts taken together shall constitute one and the same instrument.

Dated: August 28, 2020

MPH ACQUISITION HOLDINGS LLC
By:	/s/ DAVID L. REDMOND
	Name:	David L. Redmond
	Title:	Treasurer and Secretary
MPH ACQUISITION CORP.
By:	/s/ DAVID L. REDMOND
	Name:	David L. Redmond
	Title:	Treasurer and Secretary
POLARIS INTERMEDIATE CORP.
By:	/s/ DAVID L. REDMOND
	Name:	David L. Redmond
	Title:	Executive Vice President
POLARIS PARENT CORP.
By:	/s/ DAVID L. REDMOND
	Name:	David L. Redmond
	Title:	Executive Vice President

POLARIS INVESTMENT HOLDINGS, L.P.
By:	Polaris Investment Holdings GP, LLC, its general partner
By:	Hellman & Friedman Capital Partners VIII, L.P., its managing member
By:	Hellman & Friedman Investors VIII, L.P., its general partner
By:	H&F Corporate Investors VIII, LTD., its general partner
By:	/s/ HUNTER PHILBRICK
	Name:	Hunter Philbrick
	Title:	Vice President
POLARIS INVESTMENT HOLDINGS GP, LLC
By:	Hellman & Friedman Capital Partners VIII, L.P., its managing member
By:	Hellman & Friedman Investors VIII, L.P., its general partner
By:	H&F Corporate Investors VIII, LTD., its general partner
By:	/s/ HUNTER PHILBRICK
	Name:	Hunter Philbrick
	Title:	Vice President

[Joint Filing Agreement]