回复：yma16 does have a good question here..

You compute the exponent from the top to the bottom. For example
4^3^2 means 4^9 not 64^2. I wrote 4^3^2 only because WXC cannot display a lean tower of exponent. I should use your a[] notation to avoid the confusion.

If problem 1 is 1, as you mentioned the odd will have 0, (at least, five xs is 0). So problem 2 is not 1, rather it is no limit.