from itertools import product


def main():
    Ax, Ay, Bx, By, Cx, Cy = map(int, input().split())
    max_area = -1
    for a_op, b_op, c_op in product(
            [(1, 0), (-1, 0), (0, 1), (0, -1)], repeat=3):
        Point_A = (Ax + a_op[0], Ay + a_op[1])
        Point_B = (Bx + b_op[0], By + b_op[1])
        Point_C = (Cx + c_op[0], Cy + c_op[1])
        vec_AB = (Point_B[0] - Point_A[0], Point_B[1] - Point_A[1])
        vec_AC = (Point_C[0] - Point_A[0], Point_C[1] - Point_A[1])
        max_area = max(
            max_area, abs(
                vec_AB[0] * vec_AC[1] - vec_AB[1] * vec_AC[0]))
    print(max_area / 2.)


if __name__ == "__main__":
    main()