CF271D Good Substrings

You've got string $ s $ , consisting of small English letters. Some of the English letters are good, the rest are bad. A substring $ s[l...r] $ ( $ 1

N/A

N/A

In the first example there are following good substrings: "a", "ab", "b", "ba", "bab". In the second example there are following good substrings: "a", "aa", "ac", "b", "ba", "c", "ca", "cb".