Measure that distinct counts based on other columns

[Anonymous]

Hello, everyone! 

My table follows this structure:

ID	Class	CQ
111	T	00.2
111	T	00.2
111	K	00.2
222	P	00.2
222	L8	00.2
333	R1	00.2
444	H	00.1
444	K	00.1

As you can see, the values in "ID" column can have more than one occurence for each ID (can be repeated). I want to create a measure that counts all the following DISTINCT IDs values:

If Class = H or K or R1

So if a certain ID has at least one occurrence in Class column thats = H or K or R1 the measure will count it.

For the example table above, the count measure should show me 3, cause theres 3 IDs in the table that had a least 1 ocurrence of H, K or R1 in the Class column (111, 333 and  444)

Can someone help me?