courses

courses = {}

while True:
    data = input().split(" : ")
    if "end" in data:
        break
    course_name = data[0]
    student = data[1]
    if course_name not in courses:
        courses[course_name] = []
    courses[course_name].append(student)

sorted_courses = sorted(courses.items(), key=lambda kvp: -len(kvp[1]))

for k, v in sorted_courses:
    print(f"{k}: {len(v)}")
    for student in sorted(v):
        print(f"-- {student}")