Can I use more than 26 letters in `numpy.einsum`?

I am using np.einsum to multiply probability tables like:

np.einsum('ijk,jklm->ijklm', A, B)

The issue is that I am dealing with more than 26 random variables (axes) overall, so if I assign each random variable a letter I run out of letters. Is there another way I can specify the above operation to avoid this issue, without resorting to a mess of np.sum and np.dot operations?