#include <fstream>
using namespace std;
const int N = 100005;
const int MOD = 1000000007;
int main() {
	int n, D[N];
	ifstream fin("colorare3.in");
	ofstream fout("colorare3.out");
	int i, k, x ,y, sol, j;
	fin>>n>>k;
	for(i = 1; i < n; ++i) {
		fin>>x>>y;
		++D[x];++D[y];
	}
	sol = k;
	for(i = 1;i <= n; ++i)
		for(j = 1;j < D[i]; ++j)
			sol =( 1LL * sol * (k - j)) % MOD;
	fout<<sol<<'\n';
	return 0;
}