#include <iostream>
#include <iomanip>
#include <cstring>
#include <algorithm> 
#include <math.h>
#include <queue>
#include <functional>
#include <map>
#include <vector>
#include <string>
using namespace std;
typedef long long ll;
const double pi = 3.14159265359;
int main(void){
    double a, b, ans;
    cin >> a >> b;
    if (a*b >= 0) ans = 2 * pi*abs(a - b);
    else ans = 2 * pi*(abs(a) + abs(b));
    cout << fixed << setprecision(8) << ans << endl;
    
    
}