- Time limit: 1.00 s
- Memory limit: 512 MB
The first input line has two integers $n$ and $m$: the number of computers and connections. The computers are numbered $1,2,\dots,n$. Uolevi's computer is $1$ and Maija's computer is $n$.
Then, there are $m$ lines describing the connections. Each line has two integers $a$ and $b$: there is a connection between those computers.
Every connection is between two different computers, and there is at most one connection between any two computers.
If it is possible to send a message, first print $k$: the minimum number of computers on a valid route. After this, print an example of such a route. You can print any valid solution.
If there are no routes, print "IMPOSSIBLE".
- $2 \le n \le 10^5$
- $1 \le m \le 2 \cdot 10^5$
- $1 \le a,b \le n$
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