# Arup Guha
# 12/11/2024
# Solution to UCF HS Online Div 2 Problem: Pizza Party

import math

# Get input.
toks = input().split()
n = int(toks[0])
radius = int(toks[1])

# Since adjacent and due to how the cuts are, he always gets half a pizza.
# Print result. I am just doing 6 decimal places.
print(math.pi*radius*radius/2)