import numpy as np

a,b,r1, c,d,r2 = map(float, input().split())

k = np.sqrt((a-c)**2 + (b-d)**2)

c_c = ((r1**2) + (r2**2) - (k**2)) / (2*r1*r2)
s_c = np.sqrt(1 - (c_a**2))

l = r1*r2*s_c / k
c_a = 
c_d = 

s_a
s_a

 printf('%.3f', res)