#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  // https://ja.wikipedia.org/wiki/%E3%82%A4%E3%83%B3%E3%83%89%E3%82%BE%E3%82%A6#%E5%85%AC%E5%BC%8F
  long double h, r;
  cin >> h >> r;
  cout << fixed << setprecision(20) << -8.254L + 6.807L * h + 7.073L * acosl(-1) * 2 * r << endl;
  return 0;
}