2024-2025 ICPC, NERC, Southern and Volga Russian Regional Contest (Unrated, Online Mirror, ICPC Rules, Preferably Teams)

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2038 2024-2025 ICPC, NERC, Southern and Volga Russian Regional Contest (Unrated, Online Mirror, ICPC Rules, Preferably Teams) FINISHED False 18000 44479523 Nov. 18, 2024, 10:35 a.m.

Problems

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( 329 ) M Royal Flush PROGRAMMING dp implementation 2800

Consider the following game. There is a deck, which consists of cards of (n) different suits. For each suit, there are (13) cards in the deck, all with different ranks (the ranks are (2), (3), (4), ..., (10), Jack, Queen, King and Ace). Initially, the deck is shuffled randomly (all ((13n)!) possible orders of cards have the same probability). You draw (5) topmost cards from the deck. Then, every turn of the game, the following events happen, in the given order: if the cards in your hand form a Royal Flush (a (10), a Jack, a Queen, a King, and an Ace, all of the same suit), you win, and the game ends; if you haven't won yet, and the deck is empty, you lose, and the game ends; if the game hasn't ended yet, you may choose any cards from your hand (possibly, all of them) and discard them. When a card is discarded, it is removed from the game; finally, you draw cards from the deck, until you have (5) cards or the deck becomes empty. Your goal is to find a strategy that allows you to win in the minimum expected number of turns. Note that the turn when the game ends is not counted (for example, if the (5) cards you draw initially already form a Royal Flush , you win in (0) turns). Calculate the minimum possible expected number of turns required to win the game. The only line contains one integer (n) ((1 \le n \le 4)) — the number of suits used in the game. Print the minimum expected number of turns. Your answer will be considered correct if its absolute or relative error does not exceed (10^{-6}). Formally, let your answer be (a), and the jury's answer be (b). Your answer will be accepted if and only if (\frac{|a - b|}{\max{(1, |b|)}} \le 10^{-6}).

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