Exhibit A

JOINT FILING AGREEMENT

PURSUANT TO RULE 13d-1(k)(1)

The undersigned acknowledge and agree that the foregoing statement of Schedule 13G is filed on behalf of each of the undersigned and that all subsequent amendments to this statement of Schedule 13G shall be filed on behalf of each of the undersigned without the necessity of filing additional joint filing agreements. 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 Agreement may be executed in any number of counterparts and all of such counterparts taken together shall constitute one and the same instrument.

Dated: December 21, 2017

Camac Fund, LP

By: Camac Capital, LLC,

its general partner

By:

/s/ Eric Shahinian

Name: Eric Shahinian

Title: Managing Member of the GP

Camac Partners, LLC

By: Camac Capital, LLC,

its general partner

By:

/s/ Eric Shahinian

Eric Shahinian

Managing Member of the GP

Camac Capital, LLC

By:

/s/ Eric Shahinian

Eric Shahinian

Managing Member

By:

/s/ Eric Shahinian

Eric Shahinian

WUHAN GENERAL GROUP (CHINA), INC SC 13G