#
# shows the use of an if-statement and the use of a 
# parameter for a function
#
# written by e.bonakdarian   mar 2010


def printGrade(points):
    # print the correct grade based on the points
    # standard 90, 80, 70 .. distribution
    # we assume 'points' >= 0

    if points >= 90:
        print 'A'
    elif points >= 80 and points < 90:
        print 'B'
    elif points >= 70 and points < 80:
        print 'C'
    elif points >= 60 and points < 70:
        print 'D'
    else:
        print 'F'


def main():
    points = input('Enter points: ')
    printGrade(points)


main()
raw_input('\n<enter> to exit')