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CSES Problem Set

Message Route

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CSES - Message RouteCSES - Message Route

Time limit:1.00 s Memory limit:512 MB

Syrjälä's network has $n$ computers and $m$ connections. Your task is to find out if Uolevi can send a message to Maija, and if it is possible, what is the minimum number of computers on such a route.


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".


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