#include "bits/stdc++.h"

using ll = long long;

using namespace std;
#define int ll

// 0 -> a-1
#define rep(i, a) for (int i = 0; (i) < (int)(a); (i)++)
// a -> b-1
#define reps(i, a, b) for (int i = (int)(a); (i) < (int)(b); (i)++)
// a-1 -> 0
#define rrep(i, a) for (int i = (int)a - 1; (i) >= 0; (i)--)
// a-1 -> b
#define rreps(i, a, b) for (int i = (int)(a)-1; (i) >= (int)(b); (i)--)
#define MP(a, b) make_pair((a), (b))
#define PB(a) push_back((a))
#define all(v) (v).begin(), (v).end()
// next_permutation(all(v))
#define PERM(v) next_permutation(all(v))
/*sort(all(v));
(v).erase(unique(all(v)), v.end())*/
#define UNIQUE(v)                                                              \
	sort(all(v));                                                              \
	(v).erase(unique(all(v)), v.end())
#define CIN(type, x)                                                           \
	type x;                                                                    \
	cin >> x
#define YES(f)                                                                 \
	if ((f)) {                                                                 \
		cout << "YES" << endl;                                                 \
	} else {                                                                   \
		cout << "NO" << endl;                                                  \
	}
#define Yes(f)                                                                 \
	if ((f)) {                                                                 \
		cout << "Yes" << endl;                                                 \
	} else {                                                                   \
		cout << "No" << endl;                                                  \
	}
#define MINV(v) min_element(all(v))
#define MAXV(v) max_element(all(v))
#define MIN3(a, b, c) min(min(a, b), c)
#define MIN4(a, b, c, d) min(MIN3(a, b, c), d)
#define MIN5(a, b, c, d, e) min(MIN4(a, b, c, d), e)
#define MIN6(a, b, c, d, e, f) min(MIN5(a, b, c, d, e), f)
#define MAX3(a, b, c) max(max(a, b), c)
#define MAX4(a, b, c, d) max(MAX3(a, b, c), d)
#define MAX5(a, b, c, d, e) max(MAX4(a, b, c, d), e)
#define MAX6(a, b, c, d, e, f) max(MAX5(a, b, c, d, e), f)
// b is [a, c)
#define RANGE(a, b, c) ((a) <= (b) && (b) < (c))
// c is [a, e) && d is [b, f)
#define RANGE2D(a, b, c, d, e, f) (RANGE((a), (c), (e)) && RANGE((b), (d), (f)))
#define chmin(a, b) a = min(a, (b))
#define chmin3(a, b, c) a = MIN3(a, (b), (c))
#define chmin4(a, b, c, d) a = MIN4(a, (b), (c), (d))
#define chmin5(a, b, c, d, e) a = MIN5(a, (b), (c), (d), (e))
#define chmin6(a, b, c, d, e, f) a = MIN6(a, (b), (c), (d), (e), (f))
#define chmax(a, b) a = max(a, (b))
#define chmax3(a, b, c) a = MAX3(a, (b), (c))
#define chmax4(a, b, c, d) a = MAX4(a, (b), (c), (d))
#define chmax5(a, b, c, d, e) a = MAX5(a, (b), (c), (d), (e))
#define chmax6(a, b, c, d, e, f) a = MAX6(a, (b), (c), (d), (e), (f))
#define fcout cout << fixed << setprecision(12)
#define RS resize
#define CINV(v, N)                                                             \
	do {                                                                       \
		v.RS(N);                                                               \
		rep (i, N)                                                             \
			cin >> v[i];                                                       \
	} while (0);

#define RCINV(v, N)                                                            \
	do {                                                                       \
		v.RS(N);                                                               \
		rrep (i, N)                                                            \
			cin >> v[i];                                                       \
	} while (0);
#define MOD 1000000007

template <class T> inline T GET()
{
	T x;
	cin >> x;
	return x;
}

void init();
void solve();

signed main()
{
	init();
	solve();
}

template<int mod> struct ModInt {
	using ll = long long;
	int x;
	template<class T>
	ModInt(T a) {
		x = a % mod;
		if (x < 0) {
			x += mod;
		}
	}
	ModInt() : x(0) {}
	inline ModInt& operator+=(const ModInt& rhs)
	{
		(*this) += rhs.x;
		return *this;
	}
	template<class T>
	inline ModInt& operator+=(const T rhs)
	{
		x += rhs % mod;
		if (x < 0) x += mod;
		x %= mod;
		return *this;
	}
	inline ModInt& operator-=(const ModInt& rhs)
	{
		(*this) -= rhs.x;
		return *this;
	}
	template<class T>
	inline ModInt& operator-=(const T rhs)
	{
		x -= rhs % mod;
		if (x < 0) x += mod;
		x %= mod;
		return *this;
	}
	inline ModInt& operator*=(const ModInt& rhs)
	{
		(*this) *= rhs.x;
		return *this;
	}
	template<class T>
	inline ModInt& operator*=(const T rhs)
	{
		ll res = (ll) x * (rhs % mod);
		x = res % mod;
		if (x < 0) x += mod;
		return *this;
	}
	inline ModInt& operator/=(const ModInt& rhs)
	{
		(*this) /= rhs.x;
		return *this;
	}
	template<class T>
	inline ModInt& operator/=(const T rhs)
	{
		int t = rhs % mod;
		if (t < 0) t += mod;
		ll res = modpow(t);
		(*this) *= res;
		return *this;
	}
	inline ModInt& operator=(const ModInt& rhs)
	{
		(*this) = rhs.x;
		return *this;
	}
	template<class T>
	inline ModInt& operator=(const T rhs)
	{
		x = rhs % mod;
		if (x < 0) x += mod;
		return *this;
	}
	inline int operator==(const ModInt& rhs) const
	{
		return (*this) == rhs.x;
	}
	template<class T>
	inline int operator==(const T rhs) const
	{
		ModInt t(rhs);
		return (*this).x == t.x;
	}
	inline int operator!=(const ModInt& rhs) const
	{
		return (*this) != rhs.x;
	}
	inline int operator!=(const int rhs) const
	{
		ModInt t(rhs);
		return (*this).x != t.x;
	}
	inline ModInt operator++(signed unused)
	{
		ModInt res((*this).x);
		++(*this);
		return res;
	}
	inline ModInt& operator++()
	{
		(*this) += 1;
		return (*this);
	}
	inline ModInt operator--(signed unused)
	{
		ModInt res((*this).x);
		--(*this);
		return res;
	}
	inline ModInt& operator--()
	{
		(*this) -= 1;
		return (*this);
	}
	inline ModInt operator+() const
	{
		return (*this);
	}
	inline ModInt operator-() const
	{
		return (*this).x ? ModInt(mod - (*this).x) : ModInt(0);
	}
	template<class T>
	int modpow(const T val, int p = mod - 2)
	{
		if (p == 0) return 1;
		if (p % 2) return (long long) val * modpow(val, p-1) % mod;
		long long t = modpow(val, p/2);
		int res = t * t % mod;
		return res;
	}
	operator int() const
	{
		return x;
	}
	friend ostream& operator<<(ostream& lhs, const ModInt& rhs)
	{
		lhs << rhs.x;
		return lhs;
	}
	friend istream& operator>>(istream& lhs, ModInt& rhs)
	{
		long long t;
		lhs >> t;
		rhs.x = t % mod;
		if (rhs.x < 0) rhs += mod;
		return lhs;
	}
	friend const ModInt operator+(const ModInt& lhs, const ModInt& rhs)  {return ModInt(lhs) += rhs;}
	template<class T>
	friend const ModInt operator+(const ModInt& lhs, const T rhs)        {return ModInt(lhs) += rhs;}
	template<class T>
	friend const ModInt operator+(T lhs, const ModInt& rhs)              {return ModInt(lhs) += rhs;}
	friend const ModInt operator-(const ModInt& lhs, const ModInt& rhs)  {return ModInt(lhs) -= rhs;}
	template<class T>
	friend const ModInt operator-(const ModInt& lhs, const T rhs)        {return ModInt(lhs) -= rhs;}
	template<class T>
	friend const ModInt operator-(T lhs, const ModInt& rhs)              {return ModInt(lhs) -= rhs;}
	friend const ModInt operator*(const ModInt& lhs, const ModInt& rhs)  {return ModInt(lhs) *= rhs;}
	template<class T>
	friend const ModInt operator*(const ModInt& lhs, const T rhs)        {return ModInt(lhs) *= rhs;}
	template<class T>
	friend const ModInt operator*(T lhs, const ModInt& rhs)              {return ModInt(lhs) *= rhs;}
	friend const ModInt operator/(const ModInt& lhs, const ModInt& rhs)  {return ModInt(lhs) /= rhs;}
	template<class T>
	friend const ModInt operator/(const ModInt& lhs, const T rhs)        {return ModInt(lhs) /= rhs;}
	template<class T>
	friend const ModInt operator/(T lhs, const ModInt& rhs)              {return ModInt(lhs) /= rhs;}
	template<class T>
	friend const int    operator==(T lhs, const ModInt& rhs)             {return ModInt(lhs) == rhs;}
	template<class T>
	friend const int    operator!=(T lhs, const ModInt& rhs)             {return ModInt(lhs) != rhs;}
};
using modint = ModInt<1000000007>;

vector<vector<int>> v;
int N, K;

modint dfs(int n, int p, int s = 0, int t = 0) {
	modint res = (K - s - t);
	if (s >= K) return 0;
	for (auto x : v[n]) {
		if (p == x) continue;
		res *= dfs(x, n, 1, s++);
	}
	return res;
}

void init()
{
	cin >> N >> K;
	v.resize(N);
	if (N == 1) {
      cout << K << endl;
      return;
    }
	rep(i, N-1) {
		int a, b;
		cin >> a >> b;
		a--;b--;
		v[a].push_back(b);
		v[b].push_back(a);
	}
	rep(i, N) {
		if (v[i].size() == 1) {
			cout << dfs(i, -1) << endl;
			return;
		}
	}
	assert(0);
}

void solve()
{
}


Measured memory_bytes: 13568