import java.util.List;

import java.util.Set;

import java.util.HashSet;

import java.util.Iterator;

class GottaSnatchEmAll {

static Set<String> newCollection(List<String> cards) {

return new HashSet<>(cards);

}

static boolean addCard(String card, Set<String> collection) {

return collection.add(card);

}

static boolean canTrade(Set<String> myCollection, Set<String> theirCollection) {

boolean TradeBool = false;

for (String theirCard : theirCollection){

for (String myCard : myCollection){

if (!myCollection.contains(theirCard) && !theirCollection.contains(myCard)){

TradeBool = true;

break;

}

}

}

return TradeBool && !myCollection.isEmpty() && !theirCollection.isEmpty();

}

static Set<String> commonCards(List<Set<String>> collections) {

Set<String> commonCardsSet = new HashSet();

if (!collections.isEmpty()){

Iterator<Set<String>> collectionsIterator = collections.iterator();

commonCardsSet.addAll(collectionsIterator.next());

while (collectionsIterator.hasNext()){

commonCardsSet.retainAll(collectionsIterator.next());

}

}

return commonCardsSet;

}

static Set<String> allCards(List<Set<String>> collections) {

Set<String> allCardsSet = new HashSet();

for ( Set<String> collection : collections){

allCardsSet.addAll(collection);

}

return allCardsSet;

}

}