isNull Help

Made a new field "OND/LED" I want this field to show the following result if DATE 2 is blank show Date 1 if date 2 and date 1 are blank show date 3.

For Example 
Example 1:
Date 2: 01/01/17 Date 1: 11/30/16 Date 3: 12/31/17 OND/LED = 01/01/17

Example 2:
Date 2:                Date 1: 11/30/16 Date 3: 12/31/17 OND/LED = 11/30/16

Example 3:
Date 2:                Date 1:                Date 3: 12/31/17 OND/LED = 12/31/17

I tried this it didn't work:
If(isnull([Date 2],[Date 2]),isnull([Date 1},[Date 1]),[Date 3])