#include<stdio.h>
#include<stdlib.h>
//用遞歸函數(shù)來計(jì)算N的階乘
double?factorial(int?n)
{
	double?result;
	if(n<0)
	{
		printf("輸入錯(cuò)誤\n");?
	}?
	else?if(n==1?||n==0)
	{
		result=1;
	}?
	else?
	{
		result=factorial(n-1)*n;?//n=5?5-1=4?4*5=20???接下來該怎么算呢?麻煩前輩指點(diǎn)一下！?
	}?
	return?result;
}?
	
int?main?()
{
	double?n?;
	scanf("%lf",&n);?
	printf("%lf的階乘=%g\n",n,factorial(n));?
	printf("%lf的階乘=%lf\n",n,factorial(n));?
	return?0;
}