Paste: a

import java.math.BigInteger;


public class RunShuffles {
	
	private static int nCards, iCut;

	public static void main(String[] args) {
		
		nCards = Integer.parseInt(args[0]);
		iCut = Integer.parseInt(args[1]);
		//System.out.printf("nCards: %d, iCut: %d\n", nCards, iCut);
		
		int unshuffledDeck[] = new int[nCards];
		int shuffledDeck[] = new int[nCards];
		int periods[] = new int[nCards];
		int factors[] = new int[nCards];
		long start_time = System.nanoTime();
		
				
		for (int i = 0; i < nCards; i++) {
			unshuffledDeck[i] = i;
			periods[i] = -1;
			factors[i] = 0;
		}
		
		shuffledDeck = unshuffledDeck;
		//printDeck(shuffledDeck);
		
		for (int counter = 1; counter <= nCards; counter++) {
			shuffledDeck = shuffle(shuffledDeck);
			//printDeck(shuffledDeck);
			for (int i = 0; i < nCards; i++) {
				if (periods[i] == -1 && shuffledDeck[i] == i) {
					periods[i] = counter;
				}
			}
		}

		//System.out.printf("Final periods:\n");
		//printDeck(periods);
		
		BigInteger a = new BigInteger("1");
		for (int i = 0; i < nCards; i++) {
			a = lcm(a, new BigInteger(Integer.toString(periods[i])));
		}
		
		System.out.printf("lcm: %s in %d ns\n", a.toString(), System.nanoTime() - start_time);

	}
	
	public static void printDeck(int[] deck) {
		for (int i = 0; i < deck.length; i++) {
			if (iCut == i) System.out.printf("| ");
			System.out.printf("%d ", deck[i]);
		}
		System.out.printf("\n");
	}
	
	public static int[] shuffle(int[] deck) {
		int smaller_size, i, j;
		int new_deck[] = new int[nCards];
		
		if (nCards - iCut > iCut) smaller_size = iCut;
		else smaller_size = nCards - iCut;
		
		for (i = 0; i < 2*smaller_size; i+=2) {
			new_deck[nCards-i-1] = deck[iCut - i/2 - 1];
			new_deck[nCards-i-2] = deck[nCards - i/2 - 1];
		}

		i /= 2;	
		
		if (iCut - i > 0) {
		//	printf("Bottom pile was smaller\n");
			for (j = 0; j < nCards - 2*(nCards-iCut); j++) {
				new_deck[j] = deck[j];
			}
		}
		else if (nCards - iCut - i > 0) {
		//	printf("Top pile was smaller\n");
			for (j = 0; j < nCards - 2*iCut; j++) {
				new_deck[j] = deck[iCut + j];
			}
		}
		return new_deck;

	}
	
	public static BigInteger lcm(BigInteger a, BigInteger b) {
		BigInteger productAB = a.multiply(b);
		return productAB.divide(b.gcd(a));
	}

}