import sys
import math
input = sys.stdin.readline

x1, y1 = map(float, input().split())
x2, y2 = map(float, input().split())
x3, y3 = map(float, input().split())

def calc_length(x1, y1, x2, y2, x3, y3):
    r_x, r_y= (x1+x2)/2.0, (y1+y2)/2.0
    length = math.sqrt((x2-x1)**2 + (y2-y1)**2)/2.0
    length2 = math.sqrt((r_x-x3)**2 + (r_y-y3)**2)
    if length2 > length:
        return length2 - length
    else:
        return length - length2

l1 = calc_length(x1, y1, x2, y2, x3, y3)
l2 = calc_length(x1, y1, x3, y3, x2, y2)
l3 = calc_length(x2, y2, x3, y3, x1, y1)
print(round(min(l1, l2, l3),9))