def plane(a,b,c):
    """Returns the equation of a three-dimensional plane in space by entering the three coordinates of the plane."""
    p_a = (b[1]-a[1])*(c[2]-a[2])-(c[1]-a[1])*(b[2]-a[2])
    p_b = (b[2]-a[2])*(c[0]-a[0])-(c[2]-a[2])*(b[0]-a[0])
    p_c = (b[0]-a[0])*(c[1]-a[1])-(c[0]-a[0])*(b[1]-a[1])
    p_d = -1*(p_a * a[0] + p_b * a[1] + p_c * a[2])
    return p_a, p_b, p_c, p_d