To 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 no action is needed except to terminate the input loop. Any invalid input will act as a "sentinel" (terminating value such as -1) and terminate input. I need to calculate the average. MARIE doesn't have a division operator so I need to do repeated subtractions and then truncate the remainder and output a whole number.