#define _GLIBCXX_DEBUG

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

constexpr ll INF = 1e16;
constexpr ll MOD = 1000000007;

// modint: mod 計算を int を扱うように扱える構造体
template<int MOD> struct Fp {
    long long val;
    constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
        if (val < 0) v += MOD;
    }
    constexpr int getmod() { return MOD; }
    constexpr Fp operator - () const noexcept {
        return val ? MOD - val : 0;
    }
    constexpr Fp operator + (const Fp& r) const noexcept { return Fp(*this) += r; }
    constexpr Fp operator - (const Fp& r) const noexcept { return Fp(*this) -= r; }
    constexpr Fp operator * (const Fp& r) const noexcept { return Fp(*this) *= r; }
    constexpr Fp operator / (const Fp& r) const noexcept { return Fp(*this) /= r; }
    constexpr Fp& operator += (const Fp& r) noexcept {
        val += r.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
    constexpr Fp& operator -= (const Fp& r) noexcept {
        val -= r.val;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr Fp& operator *= (const Fp& r) noexcept {
        val = val * r.val % MOD;
        return *this;
    }
    constexpr Fp& operator /= (const Fp& r) noexcept {
        long long a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b; swap(a, b);
            u -= t * v; swap(u, v);
        }
        val = val * u % MOD;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr bool operator == (const Fp& r) const noexcept {
        return this->val == r.val;
    }
    constexpr bool operator != (const Fp& r) const noexcept {
        return this->val != r.val;
    }
    friend constexpr ostream& operator << (ostream &os, const Fp<MOD>& x) noexcept {
        return os << x.val;
    }
    friend constexpr istream& operator >> (istream &is, Fp<MOD>& x) noexcept {
        return is >> x.val;
    }
    friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
        if (n == 0) return 1;
        auto t = modpow(a, n / 2);
        t = t * t;
        if (n & 1) t = t * a;
        return t;
    }
};

using mint = Fp<((int)MOD)>;

#define rep(i, N) for(ll i=0; i<(N); ++i)

template<class T> inline bool chmax(T& a, T b) { if(a < b) { a = b; return 1; } else { return 0; }}
template<class T> inline bool chmin(T& a, T b) { if(a > b) { a = b; return 1; } else { return 0; }}


ll max(ll a, ll b) {return a < b ? b : a; }
ll min(ll a, ll b) {return a > b ? b : a; }
double maxf(double a, double b) { return a < b ? b : a; }

template<typename T> inline string toString(const T &a) {
  ostringstream oss; oss << a; return oss.str();
}

ll gcd(ll x, ll y) { return x % y ? gcd(y, x % y) : y; }
ll lcm(ll x, ll y) { return x * y / gcd(x, y); }

int main() {
  int N, K;
  cin >> N >> K;
  vector<vector<int>> points(N, vector<int>());
  rep(i, N - 1) {
    int a, b;
    cin >> a >> b;
    
    points[a-1].push_back(b-1);
    points[b-1].push_back(a-1);
  }
  
  queue<int> q;
  unordered_set<int> seen;
  q.push(0);
  seen.insert(0);
  mint pat = K;
  bool isfirst = true;
  while(!q.empty()) {
    int v = q.front();
    q.pop();
    
    int ni = 0;
    for(int i = 0; i < points[v].size(); ++i) {
      if(seen.find(points[v][i]) == seen.end()) {
        if(isfirst) {
          pat *= K - ni - 1;
        } else {
          pat *= K - ni - 2;
        }
        q.push(points[v][i]);
        seen.insert(points[v][i]);
        ++ni;
      }
    }
    
    isfirst = false;
  }
  
  cout << pat << endl;
}

//1 4 4 6 7 9
/*
int main() {
  int N;
  ll K;
  cin >> N >> K;
  vector<ll> A(N);
  rep(i, N) cin >> A[i];
  
  //まず，正，0，負になるペアの個数を数える
  int posct = 0;
  int zeroct = 0;
  int negct = 0;
  rep(i, N) {
    if(A[i] < 0)  ++negct;
    if(A[i] == 0) ++zeroct;
    if(A[i] > 0)  ++posct;
  }
  
  //各符号の組
  int pos_pairct = (posct * posct - posct) / 2 + (negct * negct - negct) / 2;
  int neg_pairct = negct * posct;
  int zero_pairct = (zeroct * zeroct - zeroct) / 2 + (posct * zeroct + negct * zeroct);
  
  sort(A.begin(), A.end());
  
  //順番を区別していったん数えることにする
  //同じインデックス同士は掛けないが，別のインデックスで同じ数なら掛ける
  if(K <= neg_pairct) {
    //負の領域
    //負 * 正 で二分探索
    //負を全部正にして，全部ソートすれば良いのか．筆はなくて生徒みなせばよい．順番が逆になるくらいか
    // int mid = neg_pairct / 2;
    // while(true) {
    //   if(A) 
    // }
  } else if(K <= neg_pairct + zero_pairct) {
    //ゼロの領域
    cout << 0 << endl;
    return 0;
  } else {
    //正の領域
    //昇順
    
    //二分探索で解いてみる    
    int beginIndex = -1;
    rep(i, N) {
      if(A[i] > 0) beginIndex = i;
    }
    int endIndex = N - 1;
    
    int mid = (endIndex - beginIndex) / 2 + beginIndex;
    while(true) {
       
    }
    
  }
}
*/

Measured memory_bytes: 13712