FEB

문제

Bessie and Elsie are plotting to overthrow Farmer John at last! They plan it out over $NN$ ($1\le N\le 2\cdot {10}^{5}1\backslash le\; N\backslash le\; 2\backslash cdot\; 10^5$) text messages. Their conversation can be represented by a string $SS$ of length $NN$ where $S_{i}S\_i$ is either $BB$ or $EE$, meaning the $ii$th message was sent by Bessie or Elsie, respectively.

However, Farmer John hears of the plan and attempts to intercept their conversation. Thus, some letters of $SS$ are $FF$, meaning Farmer John obfuscated the message and the sender is unknown.

The excitement level of a non-obfuscated conversation is the number of times a cow double-sends - that is, the number of occurrences of substring $BBBB$ or $EEEE$ in $SS$. You want to find the excitement level of the original message, but you don’t know which of Farmer John’s messages were actually Bessie’s / Elsie’s. Over all possibilities, output all possible excitement levels of $SS$.

입력

The first line will consist of one integer $NN$.

The next line contains $SS$.

출력

First output $KK$, the number of distinct excitement levels possible. On the next $KK$ lines, output the excitement levels, in increasing order.