#include<fstream>
#include<vector>
using namespace std;
const int maxn = 100005;
const int mod = 1000000007;

ifstream fin("colorare3.in");
ofstream fout("colorare3.out");

int i , j , a , b , n , k , dg[maxn] , ans;
bool seen[maxn];

int main()
{
	
	for( fin >> n >> k, i = 1 ; i < n ; ++i  )
			fin >> a >> b,
			dg[a]++,
			dg[b]++;
	
	ans = k;
	
	for( i = 1 ; i <= n ; ++i )
		for( j = 1 ; j < dg[i] ; ++j )
		ans = 1LL * ans * ( k - j ) % mod;
			
	fout << ans << "\n";
	
return 0;
}