What 1000000002: 90909091 should equal 1000000001??

So, in the rust version, I think I've found an issue.

In the tricky_tests, sometimes I get errors like:

With n = 18283961446061854279
Expected 18283961446061854278 but got 138 at src/lib.rs:57:9

The problem is that, as far as I've tested, in Rust and Python, 18283961446061854279 in base-138 is 1111111111.
I've collected a few of these. They were:

17126426820319058418 base-137
15705261201683973613 base-83
17393337673075145131 base-254
18412318490320479416 base-565
17948489581465697281 base-255
18283961446061854279 base-138

I have managed to submit my answer, because sometimes the tests don't use any number that breaks.