static void Main()
{
int[] input = ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
Tyoten[] tyotens = new Tyoten[input[0]];
for (int i = 0; i < tyotens.Length; i++)
{
tyotens[i] = new Tyoten((i + 1).ToString());
}
for (int i = 0; i < input[1]; i++)
{
int[] hen = ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
Tyoten.Connect(tyotens[hen[0] - 1], tyotens[hen[1] - 1]);
}
int count = 0;
List <Route> routes = new List <Route>();
routes.Add(new Route(tyotens[0]));
while (routes.Count > 0)
{
if (routes[0].UsedTyotens.Count == tyotens.Length)
{
++count;
routes.RemoveAt(0);
}
else
{
IEnumerable <Route> route = routes[0].GetNextRoutes();
if (route.Count() == 0)
{
routes.RemoveAt(0);
}
else
{
routes.RemoveAt(0);
routes.AddRange(route);
}
}
}
WriteLine(count);
ReadKey();
}
public Route(Route route, Tyoten NextPoint)
{
UsedTyotens = new List <Tyoten>(route.UsedTyotens);
NowPoint = NextPoint;
UsedTyotens.Add(NextPoint);
}
public Route(Tyoten NowPoint)
{
UsedTyotens = new List <Tyoten>();
UsedTyotens.Add(NowPoint);
this.NowPoint = NowPoint;
}
public static void Connect(Tyoten a, Tyoten b)
{
a.ConnentedTyoten.Add(b);
b.ConnentedTyoten.Add(a);
}
