Q

使用java还不熟练，错误在于读入。应用in.hasNext()

代码

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.math.BigInteger;
import java.util.Date;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws ParseException {
		Scanner in=new Scanner(System.in);
		while(in.hasNext()) {
			int n=in.nextInt();
			BigInteger ans=new BigInteger("1");
			for(int i=1;i<=n;i++) {
				BigInteger num = new BigInteger(String.valueOf(i));
				ans=ans.multiply(num);
			}
			System.out.println(ans);
		}
	}
}