from math import pi
s, d = map(float, input().split())
a = pi * (d / 2)**2
t = int(s / d)**2
r = 0
while s >= d:
    u = int(s / d)**2
    r += u
    s = (s**2 - u * a)**0.5   
    print("s :", s, "r :", r)
print(r - t)

# wasteful = int(side / diameter) ** 2

# # The frugal baker will continue until there isn't enough dough
# # including the waste around a single biscuit.
# biscuit_area = diameter ** 2 * math.pi / 4.0
# biscuit_waste = diameter ** 2 - biscuit_area
# frugal = int((side ** 2 - biscuit_waste) / biscuit_area)

# print(frugal - wasteful)


# S_biscuit = math.pi * (D ** 2) / 4 # surface d'un biscuit

# nb_biscuits = int((side / D)) ** 2 # nb biscuits de la première fournée

# reste_pate = (side ** 2) - (nb_biscuits * S_biscuit) # quantite de pate restante

# residual = reste_pate / S_biscuit # nb biscuits qu'on peut faire avec le reste

# # est-ce que le dernier biscuit fabriqué pouvait être fabriqué ?
# if (1 + residual - int(residual)) * S_biscuit < D ** 2:
#     residual -= 1

# print(int(residual))