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

import math
def d(x1, y1, x2,y2):
     return math.sqrt((x1-x2)**2 + (y1-y2)**2)
# 1 a 2
S = ((x1 + x2)/2, (y1 + y2)/2)
dist = d(x3, y3, *S) - d(x1, y1, *S) 


# 2 a 3
S = ((x2 + x3)/2, (y2 + y3)/2)
dist = min(dist, d(x1, y1, *S) - d(x2, y2, *S)) 


# 1 a 3
S = ((x1 + x3)/2, (y1 + y3)/2)
dist = min(dist, d(x2, y2, *S) - d(x1, y1, *S))

if dist < 0:
    print(-dist)
else:
    print(dist)