No.3263 Illegal Walking Path
タグ : / 解いたユーザー数 179
作問者 :
bolero
/ テスター :
のらら
ゆにたりー卿
DeltaStruct
Rice_tawara459
Andrew8128
kazuppa
よには
yimiya(いみや)
Story
Takahashi, an Earthling, had a sudden idea:
"I wanna gather 5 Iwai aliens and fuse them to create the strongest Iwai alien, the Giant Boulder alien!"
So he came to Planet Iwai as a tourist.
However, on Planet Iwai, fusing Iwai aliens is prohibited as an illegal act.
Disappointed, Takahashi was taking a walk in a park on Planet Iwai, but if he encounters Iwai aliens 5 times in a row, he will be unable to restrain his desire and will turn the Iwai aliens he met into a Giant Boulder alien.
Let's tell Takahashi whether there exists a walking path on which he will not commit the illegal act!
Problem Statement
Takahashi, an Earthling, is planning to take a walk in a park on Planet Iwai.
The park is represented by a simple connected undirected graph with $N$ vertices and $M$ edges.
The vertices are numbered vertex $1$, vertex $2$, $\dotsc$ , vertex $N$, and the $i\ (1 ≤ i ≤ M)$-th edge connects vertex $U_i$ and vertex $V_i$.
Takahashi can move in both directions between vertex $U_i$ and vertex $V_i$ through the $i$-th edge.
There are Iwai aliens at the $K$ vertices $A_1,\ A_2,\ \dotsc ,\ A_K$, and the Iwai aliens do not move between vertices.
Takahashi moves from vertex $1$ to vertex $N$.
If Takahashi encounters Iwai aliens $5$ times in a row while moving, he becomes unable to restrain his desire, so he cannot take such a route.
Specifically, when a route from vertex $1$ to vertex $N$ is represented as a vertex sequence $(v_0,\ v_1,\ \dotsc ,v_t)$, if there exists a contiguous subsequence $(v_i,\ v_{i+1},\ v_{i+2},\ v_{i+3},\ v_{i+4})$ of length $5$ consisting only of vertices with Iwai aliens, he cannot take that route.
Determine whether there exists a route on which Takahashi can move from vertex $1$ to vertex $N$.
If it exists, output the shortest distance of such a route; otherwise, output $-1$.
Constraints
- $3 \leq N \leq 10^5$
- $N - 1 \leq M \leq \min\left(\frac{N(N-1)}{2},\ 10^5 \right)$
- $1 \leq U_i < V_i \leq N $
- The given graph is simple and connected.
- $0 \leq K \leq N - 2$
- $2 \leq A_1 < A_2 < \dotsc < A_K \leq N - 1$
- All values given in the input are integers.
Input
The input is given from Standard Input in the following format.
$
N\ M \\
U_{1}\ V_{1} \\
U_{2}\ V_{2} \\
\vdots \\
U_{M} \ V_{M} \\
K \\
A_1 \ A_2 \ \dotsc \ A_K \\
$
Output
If there exists a route on which Takahashi can move from vertex $1$ to vertex $N$, output the shortest distance of such a route; otherwise, output $-1$.
Sample
Sample 1
Input
13 13 1 2 2 3 3 4 4 5 5 6 6 13 1 7 7 8 8 9 9 10 9 12 10 11 11 13 10 2 3 4 5 6 7 8 9 10 11
Output
8
A route such as $(1, 2, 3, 4, 5, 6, 13)$ cannot be taken, because he would encounter Iwai aliens $5$ times in a row.
A route such as $(1, 7, 8, 9, 12, 9, 10, 11, 13)$ does not make him encounter Iwai aliens $5$ times in a row, so he can reach vertex $N$ by it.
This route is the shortest among the routes on which he can move from vertex $1$ to vertex $N$, so the answer is $8$.
Sample 2
Input
7 6 1 2 2 3 3 4 4 5 5 6 6 7 5 2 3 4 5 6
Output
-1
No matter how he moves, Takahashi cannot restrain his desire.
Sample 3
Input
3 2 1 2 2 3 0
Output
2
There may be no Iwai aliens in the park at all.
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