#include <stdio.h>
#define nmax 100005
#define modulo 1000000007
long long i, a, b, n, k, vt[nmax], st[nmax];
long long sol, j;

int main()
{
	freopen("colorare3.in","r",stdin);
	freopen("colorare3.out","w",stdout);
	scanf("%lld %lld",&n, &k);
	for (i=1;i<n;i++)
	{
		scanf("%lld %lld",&a, &b);
		if (a>b)
			st[a]++;
		else
			st[b]++;
		vt[a]++; vt[b]++;
	}
	sol=1;
	for (i=1;i<=n;i++)
		if (k<vt[i])
		{	sol=0;	break;	}
		else
		for (j=k-vt[i]+1;j<=k-st[i];j++)
			sol=(sol*j)%modulo;
	printf("%lld",sol);
}