a=matrix([[1],[4],[2]])*matrix([[2,-1,2]])
print det(a)
U=matrix([[4,4,8,8],[0,1,2,2],[0,0,2,6],[0,0,0,2]])
print U[0,0]*U[1,1]*U[2,2]*U[3,3]
l=U.transpose()
print l
ui=U**(-1)
print ui
U.swap_rows(0,3)
U.swap_rows(1,2)
print U
print det(U)