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Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 169    Accepted Submission(s): 21


Problem Description
You are given a directed graph, which is constructed as follows:
+ Pick an connected undirected graph with exactly n vertices and n edges. The vertices are numbered 1 through n.
+ Convert each undirected edge into a directed edge, satisfying each vertice's outdegree equals 1.

Also you're given m different colors to color the vertices. Your task is to calculate the number of different colored graphs that can be made.

Two colored graphs A and B are considered the same if and only if there exists a mapping P satisfying the following constraints:

+ Vertice u in graph A has the same color as vertice P(u) in graph B.
+ For any two different vertices u and v in graph A, P(u) and P(v) are different vertices in graph B.
+ For any directed edge u -> v in graph A, there exists a corresponding directed edge P(u) -> P(v) in graph B.

Print the answer module 10^9 + 7.
 

Input
The first line contains a number T(1 <= T <= 10), denoting the number of testcases.

For each testcase, the first line contains two space-seperated integers n and m(3 <= n <= 10^5, 1 <= m <= 10^9), representing the number of vertices in the graph and the number of colors you have.

Then, n lines follow. The i-th of them contains an integer f_i, denoting a directed edge from vertice i to vertice f_i in the given graph.(1 <= f_i <= n, f_i != i)
 

Output
For each testcase, print a line containing the answer.
 

Sample Input
1 6 3 2 3 4 1 1 3
 

Sample Output
378
 

Author
学军中学
 

Source
 

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