"""
Berechnung von Zete(3)
(c) Jürgen Meier
www.3d-meier.de
21.06.2024
"""

import math

p = 0
k = 100

for n in range(0, k + 1):
    a = ((-1.0)**n) *(1.0/((7*n+1)**3)- 1.0/((7*n+2)**3)+ 1.0/((7*n+3)**3) - 1.0/((7*n+4)**3) + 1.0/((7*n+5)**3) - 1.0/((7*n+6)**3) + 1.0/((7*n+7)**3))
    p = p + a

print(4*p/3)