# include <fstream>
# include <iostream>
# define DIM 100003
# define P 1000000007
using namespace std;
int n, K, v[DIM];
long long sol=1;

void read ()
{
	ifstream fin ("colorare3.in");
	fin>>n>>K;
	int x, y;
	for(int i=1;i<n;++i)
	{
		fin>>x>>y;
		++v[x];++v[y];
	}
}

void solve ()
{
	for(int i=0;i<v[1];++i)
		sol=(sol*(K-i))%P;
	for(int i=2;i<=n;++i)
		for(int j=1;j<v[i];++j)
			sol=(sol*(K-j))%P;
	ofstream fout ("colorare3.out");
	fout<<sol;
}

int main ()
{
	read ();
	solve();
	return 0;
}