import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

public class Factorial_demo {

	public static void main(String[] args) throws Exception{
		// TODO 自动生成的方法存根
		System.out.println("输入数字：");
		int theNumber = getInt();
		int theAnswer = factorial(theNumber); 
		System.out.println("阶乘："+theAnswer);
	}
	
	public static int factorial(int n){		//递归
		if(n == 1)
			return 1;
		else
			return (n*factorial(n-1));
	}
	
	//输出方法
		public static String getString() throws IOException{
			InputStreamReader isr = new InputStreamReader(System.in);
			BufferedReader br = new BufferedReader(isr);
			String s = br.readLine();
			return s;
		}
		
		//输出方法
		public static int getInt() throws IOException{
			String s = getString();
			return Integer.parseInt(s);
		}
}