Gondola Replacement

A gondola line has $n$ cars numbered $1$ to $n$ moving on a circular track. After car $i$ passes the station, car $i+1$ passes next (and car $1$ follows car $n$). A broken car is replaced at the same spot by spare cars numbered $n+1$, $n+2$, and so on in order. A gondola sequence lists the $n$ car numbers seen at the station starting from some moment. A replacement sequence lists the original car numbers that broke, in breakdown order. Given a valid gondola sequence, output one replacement sequence that could produce it.

The first line contains $n$. The second line contains the gondola sequence of length $n$.

Print the length $l$ of the replacement sequence. If $l>0$, print the sequence on the same line separated by spaces.

• $2 \leq n \leq 100{,}000$
• The input sequence is always a valid gondola sequence.