Write a program that computes the sequential day of the year (365 or 366). (Refer to exercises 11, 12, and 13 of Chapter 7.)

The program should accept a date as month/day/year (mm/dd/yyyy).

Verify that what is entered is a valid date.

If what is entered is not a valid date, display the message Not a valid date.

Compute the day of the year using the steps below, using int arithmetic.

dayNum = 31(month 1) + day

If the month is after February subtract (4month + 23)/10.

If its a leap year (as explained in the referenced exercises) and after February 29, add 1.

Print or display the computed day of the year.

NOTE: This question is based on Chapter 7 from Python Introduction by John Zelle, 2nd Edition.