// 10-4
// 遞迴求式子和
#include <stdio.h>

double Exponential(int n, double x);

double sum(int n, double x);

int main(void)
{
	double x;			// 實數x 
	int n;				// 正整數n
	
	printf("請輸入一個實數:");
	scanf("%lf", &x);
	printf("請輸入一個正整數:");
	scanf("%d", &n);
	
	printf("f(x,n)=f(%.2f,%d)=%.2f\n", x, n, sum(n,x));	 
		
	return 0;
} 

double Exponential(int n, double x)
{
	double result;
	
	if (n == 1)
	{
		result = x;
	}
	else
	{
		result = (-x)*Exponential(n-1,x);
	}
	
	return result;
}

double sum(int n, double x)
{
	double result;
	
	if (n == 1)
	{
		result = Exponential(n,x);
	}
	else
	{
		result = Exponential(n,x)+sum(n-1,x);
	}
	
	return result;
}