- 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".
- 2 \le n \le 10^5
- 1 \le m \le 2 \cdot 10^5
- 1 \le a,b \le n
5 5 1 2 1 3 1 4 2 3 5 4
3 1 4 5