[Tex/LaTex] Typesetting nth roots when n is long

Question

Trying to take the nmth root of a results in nm overflowing off the radical sign. How can I extend the "tail" of the radical sign to contain all of nm?

Answers to similar questions suggest using the amsmath package to adjust the placement of nm, but nm is too long to fit in the space provided.

Answer 1

Hope this (\leftroot{-6}\uproot{6}) will helps:

\sqrt[\leftroot{-6}\uproot{6}nm]{a}