Java高精度学习第二弹——求N！

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

public class Main 
{
    public static void main(String []args)
    {
        Scanner cin = new Scanner(System.in);
        BigInteger a,n,i;
        while(cin.hasNext())
        {
            a = cin.nextBigInteger();
            n = BigInteger.ONE;
            for(i=BigInteger.ONE; i.compareTo(a)<=0;i=i.add(BigInteger.ONE))
                n = n.multiply(i);
            System.out.println(n);
        }
    }
}