gradesList = []
while True:
    grade = input("Anna kurssin arvosana: ")
    if grade != "":
        gradesList.append(int(grade))
    else:
        break
gradeCount = len(gradesList)
average = sum(gradesList) / gradeCount
print(f"Annoit {gradeCount} arvosanaa.")
print(f"Arvosanojen keskiarvo on {average} .")