HDU 1042 -- N! (Java)

import java.util.*;import java.math.*;public class Main {public static void main(String[] args) {Scanner in = new Scanner(System.in);while(in.hasNext()){int a=in.nextInt();BigInteger b=new BigInteger("1");for(int i=2;i<=a;i++){b=b.multiply(BigInteger.valueOf(i));}System.out.println(b);}}}