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Micro and Permutations

Problem

Editorial

Analytics

Micro is having a graph having *N* vertices numbered from *1* to *N* and *M* edges. All the edges are bidirectional. Micro wants to find out the number of lucky permutations in the graph.

A permutation of the vertices \([v_1, v_2, v_3,...., v_n ]\) is called lucky permutation, if for every vertex \(v_i \), where \(1 \le i \le N-1\), there is an edge between \(v_i\) and \(v_{i+1}\).
Help Micro find out the number of lucky permutations in the graph.

**Input:**

First line consists of two space separated integers denoting *N* and *M*.

*M* lines follow each consisting of two space separated integers *X* and *Y* denoting there is an edge between vertices numbered *X* and *Y*.

**Output:**

Print the number of lucky permutations in the graph.

**Constraints:**

\(1 \le N \le 10\)

\(1 \le M \le 100\)

\(1 \le X, Y \le N\)

Explanation

The two possible lucky permutations are 1-2-3 and 3-2-1.

Time Limit:
5.0 sec(s)
for each input file.

Memory Limit:
256 MB

Source Limit:
1024 KB

Marking Scheme:
Marks are awarded when all the testcases pass.

Allowed Languages:
C,
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Initializing Code Editor...

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