#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long t, i, j;
  t = 1;
  long long n, r;
  cin >> n >> r;
  double temp = sin(3.14159265 / n);
  double temp2 = temp / (1 - temp);
  temp2 *= r;
  cout << std::setprecision(10) << temp2;
}
