from math import pi, asin,sin


def calc(a):
    return 2 * pi * a

a = float(input())
b = float(input())
if a * b < 0:
    print(calc(abs(a)) + calc(abs(b)))
elif a == 0:
    print(calc(abs(b)))
elif b == 0:
    print(calc(abs(a)))
else:
    a = abs(a)
    b = abs(b)
    if a < b:
        a, b = b, a
    print(calc(a) - calc(b))