Item 3 of the Schedule 13D is hereby amended to read in its entirety as follows:

As of December 18, 2017, the Reporting Persons no longer beneficially own any shares of Common Stock.

Item 5 of the Schedule 13D is hereby amended to read in its entirety as follows:

The information concerning percentages of ownership set forth below is based on 76,745,948 shares of Common Stock outstanding as of November 3, 2017 in the Company’s Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2017.

Discovery Equity Partners beneficially owns 0 shares of Common Stock as of December 18, 2017, which represents 0.0% of the outstanding Common Stock.

Discovery Group beneficially owns 0 shares of Common Stock as of December 18, 2017, which represents 0.0% of the outstanding Common Stock.

Discovery Group is the investment manager of Discovery Equity Partners.   Discovery Group exercises ultimate voting and dispositive power of the securities held by Discovery Equity Partners. As a consequence, Discovery Group may be deemed to share beneficial ownership of all of the shares of Common Stock owned by Discovery Equity Partners. Voting and disposition decisions at Discovery Group with respect to the investment of such securities are made by a five-person investment committee (the “Committee”) which makes such investment decisions by majority vote. No member of the Committee may act individually to vote or sell shares of Common Stock held by Discovery Equity Partners, nor does any such member have a veto right concerning the vote or sale of any such common stock. Accordingly, no individual member of the Committee is deemed to beneficially own, and each individual member of the Committee expressly disclaims beneficial ownership of, within the meaning of Rule 13d-3, any shares of Common Stock held by Discovery Equity Partners solely by virtue of the fact that he or she is a member of the Committee.

The transactions in Common Stock effected by the Reporting Persons during the past 60 days are set out in Exhibit 1 hereto.

The Reporting Persons ceased to be beneficial owners of more than five percent of the Common Stock on December 18, 2017.

No person other than Discovery Equity Partners is known to any Reporting Person to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, any of the shares of Common Stock reported herein.

Item 6 of the Schedule 13D is hereby amended to read in its entirety as follows:

There are no contracts, arrangements, understandings or relationships (legal or otherwise) between or among any of the Reporting Persons and any other person with respect to any securities of the Company other than the governing documents of Discovery Group and Discovery Equity Partners, the margin loan facilities referred to under Item 3 above, the Joint Filing Agreement of the Reporting Persons with respect to the Schedule 13D that was included as an exhibit thereto, the Joint Filing Agreement of the Reporting Persons with respect to this Amendment No. 1 included as Exhibit 2 to this Amendment No. 1, and the Power of Attorney granted by Michael R. Murphy with respect to reports under Section 13 of the Securities Exchange Act of 1934, as amended, which Power of Attorney is included as Exhibit 3 to this Amendment No. 1.

Joint Filing Agreement dated as of December 19, 2017, by and between Discovery Equity Partners and Discovery Group.