Well, the problem says: "Output the only number — the sum of the polindrome degrees of all the string's prefixes."

So if you get the degree for every prefix you get the following:

"a" — 1; "ab" — 0; "aba" — 2; "abac" — 0; "abaca" — 0; "abacab" — 0; "abacaba" — 3;

So, the sum of all degrees is 6.

explanation of second input case as hriss95 said

BTW, I found some solutions which got AC but it gives WA on some test due to bad hashing

for example this submission 3686936 which is the first submission on status list

fails on test:

aobd

When I saw this, I thought: "7-dimensional Palindrome Degree? :O"