Petale

#include <iostream>
#include <cmath>
#include <iomanip>
#define PI 3.1415926535
using namespace std;

int main()
{
    int n,r;
    cin>>n>>r;
    cout<<fixed<<setprecision(7)<<(double)1.0*r*(sin(PI/n)/(1-sin(PI/n)));
    return 0;
}