// clang-format off
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define stoi stoll
using pii = pair<int,int>;
using vi = vector<int>;
using vvi = vector<vi>;
#define all(c) begin(c), end(c)
#define rall(c) rbegin(c), rend(c)
#define fore(x, c) for(auto &&x : c)
#define rep(i, a, n) for(int i = a, i##len = (int)(n); i < i##len; ++i)
#define rrep(i, a, n) for(int i = (int)(n - 1); i >= a; --i)
#define sz(c) ((int)c.size())
#define contains(c, x) (c.find(x) != end(c))
#define inseg(l, x, r) ((l) <= (x) && (x) < (r))
#define dump(...)
#define pb push_back
#define eb emplace_back
#define _ 0
const signed INF_ = 1001001001; const long long INF = 1001001001001001001LL;
const int DX[9] = {0,1,0,-1,1,1,-1,-1,0}, DY[9] = {-1,0,1,0,-1,1,1,-1,0};
template<class T> ostream& operator<<(ostream &os, const vector<T> &v) {
  for (auto i = begin(v); i != end(v); i++) os<<*i<<(i==end(v)-1?"":" ");return os;}
template<class T> istream& operator>>(istream &is, vector<T> &v) {
  for (auto i = begin(v); i != end(v); i++) is>>*i;return is;}
template<class T,class U> istream& operator>>(istream &is, pair<T,U> &p) {
  is>>p.first>>p.second;return is;}
template<class T, class U> bool chmax(T &a, const U &b){return a<b?a=b,1:0;}
template<class T, class U> bool chmin(T &a, const U &b){return a>b?a=b,1:0;}
template <class T> void psum(T& c) {partial_sum(begin(c), end(c), begin(c));}
template<class T> using heap = priority_queue<T, deque<T>, greater<T>>;
struct before_main_function {
  before_main_function() {
      cin.tie(nullptr); ios::sync_with_stdio(0);
      cout << setprecision(15) << fixed;
  }
} before_main_function;
// clang-format on
//------------------8<------------------------------------8<--------------------

template <int mod>
class ModInt {
 public:
  ModInt() : v(0) {}
  ModInt(int x) : v((x + mod) % mod) {}
  int value() const { return v; }
  const ModInt operator+(const ModInt &r) const {
    return ModInt(this->v + r.v);
  }
  const ModInt operator-(const ModInt &r) const {
    return ModInt(this->v + mod - r.v);
  }
  const ModInt operator*(const ModInt &r) const {
    return ModInt(this->v * r.v);
  }
  const ModInt operator/(const ModInt &r) const { return (*this * (~r)); }
  const ModInt operator^(int k) const { return ModInt(bpow(this->v, k)); }
  const ModInt operator~() const { return ModInt(bpow(this->v, mod - 2)); }
  bool operator==(const ModInt &r) const { return this->v == r.v; }
  bool operator!=(const ModInt &r) const { return this->v != r.v; }
  ModInt &operator+=(const ModInt &r) { return *this = *this + r; }
  ModInt &operator-=(const ModInt &r) { return *this = *this - r; }
  ModInt &operator*=(const ModInt &r) { return *this = *this * r; }
  ModInt &operator/=(const ModInt &r) { return *this = *this * (~r); }

 private:
  int v;
  int bpow(int a, int b) const {
    int ret = 1;
    while (b > 0) {
      if (b & 1) ret = (ret * a) % mod;
      a = (a * a) % mod;
      b >>= 1;
    }
    return ret;
  }
};
using Mint = ModInt<1000000007>;
struct Factorial {
  static constexpr int MAX_N = 2000006;
  vector<Mint> fact, fact_inv;
  Factorial(size_t size = MAX_N) : fact(size), fact_inv(size) {
    fact[0] = fact_inv[0] = 1;
    for (int i = 1; i < MAX_N; ++i) {
      fact[i] = fact[i - 1] * i;
      fact_inv[i] = ~fact[i];
    }
  }
  Mint combination(int N, int R) {
    if (N < R) return 0;
    return fact[N] * fact_inv[N - R] * fact_inv[R];
  }
  static Mint bin_pow(Mint x, int p) {
    if (x.value() == 0) return x;
    Mint prod = 1;
    while (p > 0) {
      if (p & 1) prod *= x;
      x *= x;
      p >>= 1;
    }
    return prod;
  }
} fact;

Mint P(int n, int r) { return fact.fact[n] * fact.fact_inv[n - r]; }

signed main() {
  int N, K;
  cin >> N >> K;
  vvi G(N);
  rep(i, 0, N - 1) {
    int a, b;
    cin >> a >> b;
    a--, b--;
    G[a].pb(b);
    G[b].pb(a);
  }

  auto dfs = [&](auto f, int v, int p) -> Mint {
    int ch = sz(G[v]) - 1;
    if (ch + 2 > K) {
      return Mint(0);
    }

    Mint ret = P(K - 2, ch);
    for (int w : G[v]) {
      if (w == p) continue;
      ret *= f(f, w, v);
    }
    return ret;
  };

  Mint ans = P(K, sz(G[0]) + 1);
  for (int v : G[0]) {
    ans *= dfs(dfs, v, 0);
  }
  cout << ans.value() << endl;
  return (0 ^ _ ^ 0);
}



Measured memory_bytes: 39808