"""
Aufgabe 39
(c) Jürgen Meier
www.3d-meier.de
21.12.2025
"""

import math


k = 1000000000     # Endwert Laufvariable
s = 0.0     # Summe

for k in range(0, k+1):
    a = 1.0/(3*k+1)
    b = 1.0/(3*k+2)
    s = s + (a - b)    
print(s)

#print("-------------------")
#print(math.pi/(3*math.sqrt(3)))