#include <iostream>
#include <cmath>
using namespace std;

double x;
const double PI=3.141459265;

double f(double i)
{
if (i<=1) return ((2*x)/(pow(x,2)-PI));
else return (f(i-1)*((pow(x,2)-(i-1)*pow(PI,(i-1)))/(pow(x,2)-i*pow(PI,i))));
}

int main() {
    double n;
    double S;
    cout << "x = ";
    cin >> x;
    cout << "n = ";
    cin >> n;
    S=(1/x)+f(n);
    cout << "S = " << S;
    return 0;
}