Courses

dictionary = {}

while True:
    line = input()
    if line == "end":
        break

    line_split = line.split(" : ")
    course_name = line_split[0]
    student_name = line_split[1]

    if course_name not in dictionary:
        dictionary[course_name] = []
    dictionary[course_name].append(student_name)

for course_name, students in dictionary.items():
    print(f"{course_name}: {len(students)}")

    for student in students:
        print(f"-- {student}")