from decimal import Decimal
from math import pi
from sys import stdin


def main():
    input = lambda: stdin.readline()[:-1]
    H, R = input().split()

    h, r = Decimal(H), Decimal(R)
    s = Decimal("-8.245") + Decimal("6.807") * h + Decimal("7.073") * r * 2 * Decimal(pi)
    print(s)


main()