#include <cstdio>
#include <fstream>

using namespace std;

#define m 1000000007

int n,k,x,y,i,j,v[131072];
long long s;

int main ()
{
	
	ifstream f ("colorare3.in");
	freopen ("colorare3.out","w",stdout);
	f>>n>>k;
	for(i=1;i<n;++i){
		f>>x>>y;
		++v[x];
		++v[y];
		}
	s=k;
	for(i=1;i<=n;++i)
		for(j=1;j<v[i];++j)
			s=(s*(k-j))%m;
	printf("%lld",s);
	
	return 0;}