#include<cstdio>
#include<algorithm>
#include<iostream>
#include<cmath>
#include<iomanip>
#include<cstring>
#include<vector>
#include<iterator>
#define N 10001
using namespace std;
float di(int x, int n)
{
    if(n==0) return 1;
    else if(n==1) return x;
    else
 
 return ((2*n-1)*x - di(x, n-1) -(n-1)*di(x, n-2))/n;
}
int main()
{
    int x, n;
    float c;
    cout << "請輸入x和n:";
    cin >> x >> n;
    c = di(x, n);
    cout << "P(n)x：" << c << endl;
    return 0;
}