#include<fstream>
#define Mod 1000000007
#define NN 100001

using namespace std;
ofstream out("colorare3.out");

int n,v[NN];
long long ans,k;

int main()
{
	ifstream in("colorare3.in");
	in>>n>>k;
	for(int x,y ,i=1; i<n ;++i)
	{
		in>>x>>y;
		v[x]++;
		v[y]++;
	}
	ans=k;
	for(int i=1;i<=n;i++)
		for( int j=1;j<v[i] ;j++)
			ans= ( ans* (k-j) ) % Mod;
		out<<ans<<'\n';
		return 0;
}