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:
$1 \le N \le 10$
$1 \le M \le 100$
$1 \le X, Y \le N$