import math

a = [int(i) for i in input().split(' ')]
b = [int(i) for i in input().split(' ')]
c = [int(i) for i in input().split(' ')]

s = ((a[0]+b[0])/2, (a[1]+b[1])/2)

v1 = math.sqrt((s[0]-c[0])**2 + (s[1]-c[1])**2)
r1 = math.sqrt((a[0]-b[0])**2 + (a[1]-b[1])**2)/2

a, b, c = b, c, a

s = ((a[0]+b[0])/2, (a[1]+b[1])/2)
v2 = math.sqrt((s[0]-c[0])**2 + (s[1]-c[1])**2)
r2 = math.sqrt((a[0]-b[0])**2 + (a[1]-b[1])**2)/2

a, b, c = b, c, a

s = ((a[0]+b[0])/2, (a[1]+b[1])/2)
v3 = math.sqrt((s[0]-c[0])**2 + (s[1]-c[1])**2)
r3 = math.sqrt((a[0]-b[0])**2 + (a[1]-b[1])**2)/2

print(min(abs(v1-r1), abs(v2-r2), abs(v3-r3)))