#include <cstdio>
#include <cstdlib>
using namespace std;


#define nmax 100010
#define MOD 1000000007
#define ll long long

int N, v[nmax], X, Y;
ll sol, K;

int main()
{
    freopen("colorare3.in", "r", stdin);
    freopen("colorare3.out", "w", stdout);
    int i, j;
    scanf("%i %i", &N, &K);
    for(i = 1; i < N; i++)
    {
          scanf("%i %i", &X, &Y);
          v[X] ++;
          v[Y] ++;
    }
    sol = K;
    for(i = 1; i <= N; i++)
          for(j = 1; j < v[i]; j++)
                sol = (sol * (K - j)) % MOD;
    printf("%lld\n", sol);
    return 0;
}