#include<iostream>
using namespace std;

int main()
{
	int x,n,i=0,l=0,m=1,j=1,t=1;
	float sum=1.0;
cout<<"輸入x:";

	cin>>x;
	cout<<"輸入n:";
	cin>>n;
	while(i<n)
{t*=x;
m*=j;
j+=1;
l+=1;
if(l%2==0)
sum-=t/sum;
	else
	sum+=t/sum;
	i++;}
	cout<<sum;
getchar();
system("pause");}