import math class Point: def __init__(self, x, y): self.x = x self.y = y class Triangle: def __init__(self, a, b, c): self.a = a self.b = b self.c = c def get_area(T): # TODO: 计算三角形T的面积 #海伦公式 ab = ((T.a.x-T.b.x)**2+(T.a.y-T.b.y)**2)**0.5 bc = ((T.b.x-T.c.x)**2+(T.b.y-T.c.y)**2)**0.5 ca = ((T.c.x-T.a.x)**2+(T.c.y-T.a.y)**2)**0.5 lv = (ab+bc+ca)/2 s = (lv*(lv-ab)*(lv-bc)*(lv-ca))**0.5 return s #pass def main(): x, y = map(int, input().split()) a = Point(x, y) x, y = map(int, input().split()) b = Point(x, y) x, y = map(int, input().split()) c = Point(x, y) T = Triangle(a, b, c) print("{:.2f}".format(get_area(T))) if __name__ == "__main__": main()