#https://www.nayuki.io/res/dwite-programming-contest-solutions/dwite-200410-p1.pdf
#
#
#Don't print outputs in contests
import math


x1 = 2
y1 = 4
x2 = 4
y2 = 8


r = math.sqrt((y2 - y1)*(y2 - y1) + (x2 - x1)*(x2 - x1))
a = 3.14159*r*r

print(a)




