7566: [CSES Problem Set] Message Route
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Description
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.
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.
Input
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.
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.
Output
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".
If there are no routes, print "IMPOSSIBLE".
Constraints
$2≤n≤10^5$
$1 \le m \le 2 \cdot 10^5$
$1 \le a,b \le n$
$1 \le m \le 2 \cdot 10^5$
$1 \le a,b \le n$
Sample 1 Input
5 5
1 2
1 3
1 4
2 3
5 4
Sample 1 Output
3
1 4 5