EXHIBIT 99.1

February 14, 2018

In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of
1934, as amended, Zuckerman Investment Group, LLC, ZIG Holding, LLC,
Sherwin A. Zuckerman and Daniel R. Zuckerman each hereby agree to the joint
filing of this statement on Schedule 13G (including any and all amendments
hereto). In addition, each party to this Agreement expressly authorizes
each other party to this Agreement to file on its behalf any and all
amendments to such Statement on Schedule 13G. A copy of this Agreement
shall be attached as an exhibit to the Statement on Schedule 13G filed
on behalf of each of the parties hereto, to which this Agreement relates.

This Agreement may be executed in multiple counterparts, each of which
shall constitute an original, one and the same instrument.

ZUCKERMAN INVESTMENT GROUP, LLC

By:    /s/ Daniel R. Zuckerman
Name:  Daniel R. Zuckerman
Its: Co-CEO

ZIG Holding, LLC
By: /s/ Sherwin A. Zuckerman
Name:   Sherwin A. Zuckerman
Its:  Manager

/s/ Sherwin A. Zuckerman
Sherwin A. Zuckerman

/s/ Daniel R. Zuckerman
Daniel Zuckerman