There are $$52$$ cards in a deck.  Every $$13$$ cards form a same pattern.  Each pattern is labelled  $$A$$, $$2$$, $$3$$, $$4$$, $$5$$, $$6$$, $$7$$, $$8$$, $$9$$, $$10$$, $$J$$, $$Q$$, $$K$$.  At least how many cards must be drawn to ensure there is a card labelled "$$A$$"? 
Overseas Competition->Knowledge Point->Counting Modules->Permutations and Combinations->Combinations Overseas Competition->Knowledge Point->Combinatorics->Pigeonhole Principle->Worst Case in Pigeonhole Principle Problems