#!/usr/bin/python2
# -*- coding: utf-8 -*-
# †
from math import pi

# [0, x] の範囲の表面積。x >= 0 であること
def f(x):
    return 2 * pi * x

def sign(x):
    if x == 0:
        return 1
    return abs(x) / x

a = float(raw_input())
b = float(raw_input())
if sign(a) == sign(b):
    mini, maxi = sorted([abs(a), abs(b)])
    res = f(maxi) - f(mini)
else:
    res = f(abs(a)) + f(abs(b))
print res