- Time limit: 1.00 s
- Memory limit: 512 MB
A game consists of n rooms and m teleporters. At the beginning of each day, you start in room 1 and you have to reach room n.
You can use each teleporter at most once during the game. You want to play the game for exactly k days. Every time you use any teleporter you have to pay one coin. What is the minimum number of coins you have to pay during k days if you play optimally?
The first input line has three integers n, m and k: the number of rooms, the number of teleporters and the number of days you play the game. The rooms are numbered 1,2,\dots,n.
After this, there are m lines describing the teleporters. Each line has two integers a and b: there is a teleporter from room a to room b.
There are no two teleporters whose starting and ending room are the same.
First print one integer: the minimum number of coins you have to pay if you play optimally. Then, print k route descriptions according to the example. You can print any valid solution.
If it is not possible to play the game for k days, print only -1.
- 2 \le n \le 500
- 1 \le m \le 1000
- 1 \le k \le n-1
- 1 \le a,b \le n
8 10 2 1 2 1 3 2 5 2 4 3 5 3 6 4 8 5 8 6 7 7 8
6 4 1 2 4 8 4 1 3 5 8