#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;
//using mint = modint1000000007;
//using mint = modint998244353;

// シュリクマー関数(インドゾウの表面積)
// h: 肩までの高さ、r: 前足の半径
double sreekumar(double h, double r){
  double pi = acos(0) * 2.0;
  double ret = -8.245 + 6.807 * h + 7.073 * (2.0 * pi * r);
  return ret;
}


int main(){
  double H, R;
  cin >> H >> R;

  printf("%.12lf\n", sreekumar(H, R));
  
  return 0;
}