a -> no successor
12 -> 21
03snd3fk5ee2 -> 03snd3fke25e
gfedcba987 -> no successor
036420 -> 040236
09876543210 -> 10023456789
a0a -> aa0
0aa -> a0a
0123456789abcdefghijklmnopqrstuvwxyz -> 0123456789abcdefghijklmnopqrstuvwxzy
0 -> no successor
z -> no successor
0zyxwvutsrqponmlkjihgfedcba9876543210 -> 10023456789abcdefghijklmnopqrstuvwxyz
aaaaaaaaaaaa -> no successor
abbbbbbbbbbb -> babbbbbbbbbb
098yq345lkbjsvd098awyu4h5oikzhufg098u4wy5 -> 098yq345lkbjsvd098awyu4h5oikzhufg098u4y5w