"""
Berechnung von Zeta(3)
(c) Jürgen Meier
www.3d-meier.de
05.07.2024
"""

import math


p = 0
k = 1000
for n in range(0, k + 1):
    p = p + 1.0/((2*n+1)**3)

print(8.0*p/7)