                                                                       Exhibit 1

                  AGREEMENT AS TO JOINT FILING OF SCHEDULE 13D

                             Dated January 26, 2006

The undersigned acknowledge and agree that the foregoing statement on Schedule
13D is filed on behalf of each of the undersigned and that all subsequent
amendments to this statement 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 counterparts and each of such
counterparts taken together shall constitute one and the same instrument.


                                       BLUE HARBOUR STRATEGIC VALUE
                                       PARTNERS MASTER FUND, LP

                                       By:  Blue Harbour GP, LLC,  its
                                            general partner


                                           By:    /s/ Clifton S. Robbins
                                                  ------------------------------
                                           Name:   Clifton S. Robbins
                                           Title:  Managing Member


                                       BLUE HARBOUR GP, LLC

                                       By:     /s/ Clifton S. Robbins
                                               ---------------------------------
                                       Name:   Clifton S. Robbins
                                       Title:  Managing Member

                                       BLUE HARBOUR GROUP, LP

                                       By:  Blue Harbour Holdings, LLC, its
                                            general partner

                                           By:    /s/ Clifton S. Robbins
                                                  ------------------------------
                                           Name:  Clifton S. Robbins
                                           Title: Managing Member

                                       BLUE HARBOUR HOLDINGS, LLC

                                       By:    /s/ Clifton S. Robbins
                                              ----------------------------------
                                       Name:  Clifton S. Robbins
                                       Title: Managing Member


                                              /s/ Clifton S. Robbins
                                              ----------------------------------
                                       Name:  Clifton S. Robbins
