import math

def distance(x1, y1, x2, y2):
    return math.sqrt((x1-x2)**2+(y1-y2)**2)

def calculate(x1,y1,x2,y2,x3,y3):
    xm = (x1+x2)/2
    ym = (y1+y2)/2

    r = distance(x1,y1, x2, y2)/2
    return abs(r-distance(xm, ym, x3,y3))




def solve():
    x1, y1 = map(int, input().split())
    x2, y2 = map(int, input().split())
    x3, y3 = map(int, input().split())
    
    print(min(calculate(x1,y1,x2,y2,x3,y3),calculate(x2,y2,x3,y3,x1,y1),calculate(x3,y3,x1,y1,x2,y2)))

solve()