Bessie and Elsie are plotting to overthrow Farmer John at last! They plan it out
over \(N\) (\(1\le N\le 2\cdot 10^5\)) text messages. Their conversation can be
represented by a string \(S\) of length \(N\) where \(S_i\) is either \(B\) or \(E\),
meaning the \(i\)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 \(S\) are \(F\), 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 \(BB\)
or \(EE\) in \(S\). 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
\(S\).

Problem credits: William Yue and Claire Zhang

SCORING

• Inputs 4-8: \(N\le 10\)
• Inputs 9-20: No additional constraints.

Problem credits: William Yue and Claire Zhang

The first line will consist of one integer \(N\).

The next line contains \(S\).

First output \(K\), the number of distinct excitement levels possible. On the next
\(K\) lines, output the excitement levels, in increasing order.

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