#include <cstdio>
#define X 1000000007

int n, k, v[100010];
long long sol;

int main()
{
	freopen("colorare3.in","r",stdin);
	freopen("colorare3.out","w",stdout);
	scanf("%d %d",&n,&k);
	int i, x, y, c;
	for (i=1; i<n; i++) 
	{
		scanf("%d %d",&x,&y);
		v[x]++;
		v[y]++;
	}
	sol=k;
	for (i=1; i<=n; i++)
		for (c=k-1; c>=k-v[i]+1; c--) sol=sol*c%X;
	printf("%d\n",sol);
}