How to give value to field form other fields used in SSIS trasformation?

Hi All,

I have 36 fields(SINGLE_PREM_X, X = 1 to 36) in output file(.txt file) to create. All fields contain some numeric value. Few of them(12 fields) have to map with input fields from the table(which is already available/created) and rest of them(24 fields) I have to set 0 values in derived column in SSIS.

I have one more field name (NO_SINGLE_PREM) to get in output file and I have to set(give) this field like "This is equal to the number of array elements (SINGLE_PREM_X) filled with a value greater than 0."

Please tell me how can I get integer value for field name NO_SINGLE_PREM.

In my SSIS package, I have OLE DB source, Derived column and flat file destination set up.  

Thanks for the help in advance.

Vicky