#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1);
int main() {
  int n;
  double R, r;
  double st;
  while (scanf("%d %lf", &n, &R) != EOF) {
    st = pi / (1.0 * n);
    r = sin(st) * R / (1 - sin(st));
    printf("%.7lf\n", r);
  }
  return 0;
}
