#include <stdio.h>
#define nmax 100005
long long n, a, b, i, inc, sf, rez, nr[nmax], j, k;
int main()
{
	freopen("colorare3.in","r",stdin);
	freopen("colorare3.out","w",stdout);
	scanf("%ld %ld",&n, &k);
	for (i=1;i<=n-1;i++)
	{
		scanf("%ld %ld",&a, &b);
		nr[a]++; nr[b]++;
	}
	rez=1;
	for (i=1;i<=n;i++)
	{
		sf=k-1+(i==1);
		for (j=k-nr[i]+1;j<=sf;j++)
			rez=(rez*j)%1000000007;
	}
	printf("%ld",rez);
	return 0;
}