#include <cstdio>
#include <vector>
const int N = 100005;
const int MOD = 1000000007;
int main() {
	int n, D[N];
	freopen("colorare3.in", "r", stdin);
	freopen("colorare3.out", "w", stdout);
	int i, k, x ,y, sol, j;
	scanf("%d %d", &n, &k);
	for(i = 1; i < n; ++i) {
		scanf("%d %d", &x, &y);
		++D[x];++D[y];
	}
	sol = k;
	for(i = 1;i <= n; ++i)
		for(j = 1;j < D[i]; ++j)
			sol =( (long long) sol * (k - j)) % MOD;
	printf("%d", sol);
	return 0;
}