from math import sqrt, acos, pi, cos

X1, Y1 =  map(int, input().split())
X2, Y2 =  map(int, input().split())
X3, Y3 =  map(int, input().split())

b1 = (X1, Y1)
b2 = (X2, Y2)
b3 = (X3, Y3)

def dst(x,y):
    return sqrt((x[0] - y[0])**2 + (x[1] - y[1])**2)

def product(x,y):
    return x[0]*y[0] + x[1]*y[1]

def solution(x, y1, y2):
    m = ((y1[0] + y2[0])/2, (y1[1] + y2[1])/2)
    r = dst(y1, y2)/2
    return abs(dst(x,m) - r)

print(min(solution(b1, b2, b3), solution(b2, b1, b3), solution(b3, b1, b2)))


#l1 = dst(b1, b2)
#l2 = dst(b3, b2)
#
#
#
#l_min = l1
#
#if l1 > l2:
#    l_min = l2
#
#b1_norm = (b1[0] - b2[0], b1[1] - b2[1])
#b2_norm = (b3[0] - b2[0], b3[1] - b2[1])
#
#beta = acos(product(b1_norm, b2_norm)/(l1*l2))
#
#beta_new = beta%(pi/2)
#
#alpha = 90 - beta_new
#
#print(l_min*cos(alpha))
#