//编写一个程序计算3!+6!+9!+12!+15!+18!+21!的和是多少
#include<stdio.h>
double fun(int x)
{
    if(x==1)
		return 1;
	else 
		return x*fun(x-1);

}
int main()
{
   int i;
   double n,sum=0;
   for(i=3;i<=21;i+=3)
   {
	   n= fun(i);
	   printf("%lf\n",n);
	   sum+=n;
   }
   printf("3!+6!+9!+12!+15!+18!+21!=%-3lf\n",sum);
   
   return 0;

}