# counts the # of A’s (scores between 90 and 100)
# B's, C's, D's, and F's

grades = [90,100,70,45,76,84,93,21,36,99,100]

# create counter variables
a = 0
b = 0
c = 0
d = 0
f = 0

# start iterating through list
# check in which range each grade lies
# and add to appropriate counter
for grade in grades:
    if grade > 90:
        a += 1
    elif 80 < grade <= 90:
        b += 1
    elif 70 < grade <= 80:
        c += 1
    elif 65 < grade <= 70:
        d += 1
    else:
        f += 1

# output
print ("A's: ", a)
print ("B's: ", b)
print ("C's: ", c)
print ("D's: ", d)
print ("F's: ", f)