Need a count of this Interbase Distinct SQL

I have the following working Distinct Interbase SQL on the two fields. I need to modify it to just return a count of these distinct records.

select distinct ap.propertyuid, ap.adjpropertyuid
from adjproperty ap
where ap.payyear = 2019
order by 1, 2

Data

propertyUID adjpropertyUID payyear

15 21 2019

15 22 2019

16 23 2019

16 23 2019

16 25 2019

17 33 2019

17 33 2019

Should return a count of five,

select count(distinct ap.propertyuid || ap.adjpropertyuid)
  from adjproperty ap
 where ap.payyear = 2019