#include <cstdio>

#define modulo 1000000007
#define Nmax 100001

int N, K, i, j, nr, x, y;
int g[Nmax];

int main()
{
 freopen("colorare3.in","r",stdin);
 freopen("colorare3.out","w",stdout);
 
 scanf("%d %d",&N,&K);
 for (i=1; i<N; ++i)
     {
      scanf("%d %d",&x,&y);
      ++g[x], ++g[y];
     }
 
 for (i=1, nr=K; i<=N && nr!=0; ++i)
     for (j=1; j<g[i] && j<=K; ++j)
         nr = ((long long) nr * (K-j)) % modulo;
 
 printf("%d\n",nr);
 
 return 0;
}