#-------------------------------------------------------------------------------
# Name:        mÃ³dulo1
# Purpose:
#
# Author:      FliaSalinasRodriguez
#
# Created:     08/04/2018
# Copyright:   (c) FliaSalinasRodriguez 2018
# Licence:     <your licence>
#-------------------------------------------------------------------------------
import math
x1=float(input("x1:"))
y1=float(input("y1:"))
x2=float(input("x2:"))
y2=float(input("y2:"))

rad=(((math.sqrt((x2-x1)**2+(y2-y1)**2)/(3.1416*2))))
print("radio circunferencia:")
print(rad)