Fern, Inc., Ivy, Inc., and ABC, Inc. formed Big Tree General Partnership. Fern owns a 50% interest and Ivy and ABC each own 25% interests. Fern, Inc. files its tax return on an October 31 year-end; Ivy, Inc., files with a May 31 year-end, and ABC, files with a November 30 year-end. What is the least aggregate number of deferred months and the required taxable year-end for Big Tree General Partnership?