#include<stdio.h>
#include<iostream>
#include<vector>
#include<math.h>
#include<iomanip>
using namespace std;
int main(){
    double H,R;
    cin>>H>>R;
    double S=-8.245+6.807*H+7.073*2*R*acos(-1);
     cout << fixed << setprecision(10) << S << endl;
return 0;}