Develop a MARIE program that will input a variable number of user entered Decimal whole number grades, validating each one (0-100) in a subroutine. If the input is invalid just terminate the input loop. So, any invalid input will act as a "sentinel" (terminating value such as -1) and terminate input. Then calculate the average. MARIE doesn't have a division operator so you will need to do repeated subtractions. Just truncate the remainder and output a whole number.