public List<String> getMostValuableItemNames(List<UserWithItems> users) {
        return users.stream()
                .flatMap(u -> u.getItems().stream())
                .sorted()
                .distinct()
                .map(Item::getName)
                .collect(toList());
    }

    @Data
    static class UserWithItems {
        private final List<Item> items;
    }

    @Data
    static class Item implements Comparable<Item> {

        private final int value;
        private final String name;

        @Override
        public int compareTo(Item o) {
            return Integer.compare(value, o.value);
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            Item item = (Item) o;
            return value == item.value &&
                    Objects.equals(name, item.name);
        }

        @Override
        public int hashCode() {
            return Objects.hash(value, name);
        }
    }