It's Mooin' Time timer 1s memory 1024MB

Farmer John is trying to describe his favorite USACO contest to Elsie, but she is having trouble understanding why he likes it so much. He says "My favorite part of the contest was when Bessie said 'It's Mooin' Time' and mooed all over the contest."

Elsie still doesn't understand so Farmer John downloads the contest as a text file and tries to explain what he means. The contest is defined as a string of lowercase letters of length N (3 \leq N \leq 20\,000). A moo is generally defined as the substring c_ic_jc_j where some character c_i followed directly by 2 occurrences of some character c_j where c_i \neq c_j. According to Farmer John, Bessie moos a lot, so if some moo appears at least F (1\le F\le N) times in the contest, that might be from Bessie.

However, Farmer John's download might have been corrupted, and the text file might have up to one character that differs from the original file. Print all possible moos that Bessie could have made taking the potential error into account, sorted in alphabetical order.