import java.util.*;

class User {
    private Integer id;
    private String name;
    private Set<User> followers;
    private Set<User> following;

    public User(Integer id, String name) {
        this.id = id;
        this.name = name;
        this.followers = new HashSet<>();
        this.following = new HashSet<>();
    }

    public String getName() {
        return name;
    }

    // Receive notification
    public void update(String message, User followee) {
        System.out.println(name + " received notification: " +
                followee.getName() + " posted: \"" + message + "\".");
    }

    public void addFollower(User user) {
        followers.add(user);
    }

    public void removeFollower(User user) {
        followers.remove(user);
    }

    public void notifyFollowers(String message) {
        for (User follower : followers) {
            follower.update(message, this);
        }
    }

    public void post(String content) {
        System.out.println(name + " posted: \"" + content + "\".");
        notifyFollowers(content);
    }

    public void follow(User user) {
        following.add(user);
        user.addFollower(this);
    }

    public void unfollow(User user) {
        following.remove(user);
        user.removeFollower(this);
    }
}

class Platform {
    private Map<Integer, User> users;

    public Platform() {
        users = new HashMap<>();
    }

    public void addUser(Integer id, String name) {
        User user = new User(id, name);
        users.put(id, user);
        System.out.println(name + " added successfully.");
    }

    public void follow(Integer followerId, Integer followeeId) {
        User follower = users.get(followerId);
        User followee = users.get(followeeId);

        if (follower != null && followee != null) {
            follower.follow(followee);
            System.out.println(follower.getName() +
                    " is now following " + followee.getName() + ".");
        }
    }

    public void unfollow(Integer followerId, Integer followeeId) {
        User follower = users.get(followerId);
        User followee = users.get(followeeId);

        if (follower != null && followee != null) {
            follower.unfollow(followee);
            System.out.println(follower.getName() +
                    " has unfollowed " + followee.getName() + ".");
        }
    }

    public void post(Integer userId, String content) {
        User user = users.get(userId);
        if (user != null) {
            user.post(content);
        }
    }
}