Олимпиадный тренинг

Задача 21951. British scientists and Vasily


Задача

Темы:
According to the rezulattas, there is an example of one English unviertiset, not ieemt zachneiya, in the cookery, the bkuvy in the salt are right. Galvone, chotby preav and ploendya bkvuy blyi on the site. Osatlyne bkuvy mgout seldovt in a plonm bsepordyak, everything is torn tkest chtaitseya without straps. Pichryony this is the fact that we do not read the same letter in a single note, but the whole solvo clique.

Inspired by the study of British scientists on human perception of the text, Vasya decided that modern writing needs serious simplification. In particular, in Vasya's lexicon all words consist only of letters a, b and c. In addition, Vasya's memory is poor, so Vasya only remembers words that contain no more than L letters.

Moreover, since our young friend spilled coffee on his beloved laptop, he has not bothered to press the spacebar (explaining this by the fact that the absence of spaces in the text does not interfere with his understanding at all). However, the rest of the keyboard keys work properly, which allows Vasya to type all the words he knows without a single spelling mistake.

British scientists became very interested in Vasya's research. They entered into an active correspondence with the young scientist, however, having received another message from Vasino, they were somewhat puzzled by what he meant. Since they could not figure it out, and the next revolutionary discovery had already been announced in the media, they decided to somehow assess the level of the author's genius. To do this, they decided to understand what is the minimum number of words that Vasily's vocabulary can consist of?

Input data format
The first line of the input contains an integer L — the maximum length of a word that can be contained in Vasya's lexicon (1 <= L <= 10,000). The next line contains a non-empty message received by the scientists. The length of the message does not exceed 20,000 characters.

Output data format
In the first line print a single number K — the minimum number of words that Vasily must know in order to write this message. In the next K lines print the words themselves, each of which must have a length not exceeding L. If there are several answers, it is allowed to print any of them.

Example
Input:
3
ababaabab

Output:
2
aba
ab

Remark
In the first example from the condition, one of the possible ways to interpret Vasya's message is: ab aba ab ab.