from math import *


def S(a, b, c):
    p = (a+b+c)/2
    ans = (p*(p-a)*(p-b)*(p-c))**0.5
    return round(ans, 2)


def dis(a, b):
    return sqrt((a[0]-b[0])**2+(a[1]-b[1])**2)


s = []
for i in range(3):
    s.append(list(map(float, input().split())))

a = dis(s[0], s[1])
b = dis(s[1], s[2])
c = dis(s[2], s[0])
print("{:.2f}".format(S(a, b, c)))