package AssociativeArraysExercise;

import java.util.*;

import static java.util.stream.Collectors.toMap;

public class Courses {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        Map<String, ArrayList<String>> courses = new LinkedHashMap<>();

        String input = " ";

        while (!"end".equals(input = scanner.nextLine())) {

            String[] data = input.split(" : ");
            String course = data[0];
            String student = data[1];

            if (!courses.containsKey(course)) {
                courses.put(course, new ArrayList<>());
                courses.get(course).add(student);
            } else {
                courses.get(course).add(student);
                Collections.sort(courses.get(course));
            }
        }

        Map<String, List<String>> sorted = courses.entrySet().stream()
                .sorted((e1,e2) -> Integer.compare(e2.getValue().size(), e1.getValue().size()))
                .collect(toMap(
                        Map.Entry::getKey,
                        Map.Entry::getValue,
                        (a,b) -> {throw new AssertionError();},
                        LinkedHashMap::new
                ));

        for (Map.Entry<String,List<String>> course : sorted.entrySet()) {
            System.out.println(String.format("%s: %d",course.getKey(), course.getValue().size()));

            List<String> studentNames = course.getValue();
            for (String name: studentNames) {
                System.out.println(" -- " + name);
            }
        }


    }
}