#include <bits/stdc++.h>
using namespace std;
double N, R;
int main(void) {
  cin >> N >> R;
  double val = sin(3.14159265358979323846 / N);
  double rad = 1 / (1 / val - 1);
  rad *= R;
  printf("%0.12lf\n", rad);
  return 0;
}
