Flow Schedule type fast formula to schedule a HCM extract for every 3rd monday of the Month

Hi,

I am trying to build the fast formula to schedule the extract every 3rd Monday of the month. Below is the formula written by me. But I am getting type cast error in line 3.

INPUTS ARE SUBMISSION_DATE(DATE), SCHEDULED_DATE(DATE), V_SCHEDULE_DATE(DATE)

IF TO_CHAR(TRUNC((ADD_DAYS(SCHEDULED_DATE,20)),'MM'),'DAY')='1'

THEN V_SCHEDULE_DATE=NEXT_DAY(TRUNC(SCHEDULED_DATE,'MM')+7,'1')

ELSE V_SCHEDULE_DATE=NEXT_DAY(TRUNC(SCHEDULED_DATE,'MM')+14,'1')

NEXT_SCHEDULED_DATE=V_SCHEDULE_DATE

RETURN NEXT_SCHEDULED_DATE

Any help will be appreciated.