FactorialDivisionTsvetelin

/*
 * 19/46/2018 at 18:46:43
 * FactorialDivision.java created by Tsvetelin
 */
package Methods_Excerices;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Scanner;

/**
 * @author Tsvetelin
 *
 */
public class FactorialDivision
{

    /**
     * @param args
     */
    public static void main ( String [] args )
    {
        Scanner in = new Scanner( System.in );

        int a = Integer.parseInt( in.nextLine() );
        int b = Integer.parseInt( in.nextLine() );

        boolean positiveA = a>0; a = Math.abs( a );
        boolean positiveB = b>0; b = Math.abs( b );

        BigInteger factA = positiveA
                ? factorial( new BigInteger( a + "" )  )
                : BigInteger.ZERO.subtract( factorial( new BigInteger( a + "" ) ) );
        BigInteger factB = positiveB
                ? factorial( new BigInteger( b + "" ) )
                : BigInteger.ZERO.subtract( factorial( new BigInteger( b + "" ) ) );

        System.out.printf( "%.2f", divide( factA, factB ) );
    }

    /**
     * @param a
     * @param b
     * @return
     */
    private static BigDecimal divide ( BigInteger a , BigInteger b )
    {

        return new BigDecimal( a.divide( b ) );
    }

    /**
     * @param a
     * @return
     */
    private static BigInteger factorial ( BigInteger a )
    {
        if(a.compareTo( BigInteger.ZERO ) == 0) return BigInteger.ONE;
        else return a.multiply( factorial( a.subtract( BigInteger.ONE ) ) );

    }

}