from math import hypot
import sys

x1, y1 = map(int, sys.stdin.readline().split())
x2, y2 = map(int, sys.stdin.readline().split())
x3, y3 = map(int, sys.stdin.readline().split())

v1 = (x1 - x2, y1 - y2)
v2 = (x1 - x3, y1 - y3)
v3 = (x2 - x3, y2 - y3)
vp1 = (v1[0] / 2, v1[1] /2 )
vp2 = (v2[0] / 2, v2[1] /2 )
vp3 = (v3[0] / 2, v3[1] /2 )

s1 = (x2 + vp1[0], y2 + vp1[1])
s2 = (x3 + vp1[0], y3 + vp1[1])
s3 = (x3 + vp3[0], y3 + vp3[1])

res = abs(min( hypot(s1[0] - x3, s1[1] - y3) - hypot(vp1[0], vp1[1]), hypot(s2[0] - x2, s2[1] - y2) - hypot(vp2[0], vp2[1]),hypot(s3[0] - x1, s3[1] - y1) - hypot(vp3[0], vp3[1])))
print("%.9f"%(res))