#include<iostream>
#include<string>
#include<algorithm>
#include<cstdlib>
#include<cmath>
#include<vector>
#include<list>
#include<cstdint>
#include<bits/stdc++.h>
#include<queue>
#include<set>

#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define rep_r(i, n) for(int i = n-1; i >= 0; i--)
#define rep1(i, n) for(int i = 1; i <= (int)(n); i++)
#define REP(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define all(x) (x).begin(),(x).end()
#define SZ(x) ((ll)(x).size())
#define bit(n) (1LL<<(n))
#define UNIQUE(v) v.erase( unique(v.begin(), v.end()), v.end() );

#define INF bit(60)
#define pb push_back
#define mod 1000000007

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

using namespace std;
using uif=uint_fast64_t;
using ll=long long int;

int qp(int a,ll b){int ans=1;do{if(b&1)ans=1ll*ans*a%mod;a=1ll*a*a%mod;}while(b>>=1);return ans;}
int qp(int a,ll b,int mo){int ans=1;do{if(b&1)ans=1ll*ans*a%mo;a=1ll*a*a%mo;}while(b>>=1);return ans;}

int gcd(int a,int b){return b?gcd(b,a%b):a;}
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};


#define FACSIZE 200002

ll invfac[FACSIZE];
ll fac[FACSIZE];

ll mod_pow(ll ,ll );
ll mod_add(ll ,ll );
ll mod_mul(ll ,ll );
ll mod_div(ll ,ll );
void make_fact(ll );
void make_invfact(ll );

struct Node{

  Node* parent=nullptr;
  vector<Node*> next;
  ll ind;
  //ll val;
  bool been=false;

};

ll N,k;

ll dfs(Node* node){
  //cout << (int)node->been << endl;
  node->been=true;
  //cout << node->ind << endl;
  //cout << node->parent->ind << endl;
  //if(node->parent->ind==0) cout << node->next.size() << endl;
  //else cout << node->next.size()-1 << endl;
  
  if( node->parent->ind!=0 && node->next.size()-1==0 ) return 1LL;

  ll tmp;
  if(node->parent->ind==0){
    //cout << "k:" << k << endl;
    //cout << k-1 << endl;
    //cout << k-1 - (node->next.size()) << endl;
    //cout << "fac:" << fac[k-1] << endl;
    //cout << "fac_div:" << fac[ k-1 - (node->next.size()) ] << endl;
    tmp=mod_div( fac[k-1],fac[k-1 - (node->next.size()) ] );
  } 
  else{
    //tmp=node->next.size();
    //cout << "k:" << k << endl;
    //cout << k-2 << endl;
    //cout << k-2 - (node->next.size()-1) << endl;
    //cout << "fac:" << fac[k-2] << endl;
    //cout << "fac_div:" << fac[ k-2 - (node->next.size()-1) ] << endl;
    tmp=mod_div( fac[k-2],fac[k-2 - (node->next.size()-1) ] );
    
  }
  //cout << tmp << endl;
  //cout << endl;

  //if(tmp==0) return 1LL;

  for(auto nn:node->next){
    if( nn->been ) continue;
    else{
      nn->parent = node;
      tmp=mod_mul(tmp,dfs(nn));
    }
  }
  return tmp;
}

int main(void){

  
  cin>>N>>k;

  if(N==1){
    cout << k << endl;
    return 0;
  }
  
  

  vector<Node> v(N+1);
  rep(i,N+1) v[i].ind=i;

  rep(i,N-1){
    ll a,b;
    cin>>a>>b;
    v[a].next.pb( &v[b]);
    v[b].next.pb( &v[a]);

  }

  make_fact(FACSIZE-2);
  make_invfact(FACSIZE-2);

  rep1(i,N){
    if( v[i].next.size() > k-1 ){
      cout << 0 << endl;
      return 0;
    }
  }

  //cout << "FACT:" << fac[20] << endl;
  //rep(i,20) cout << "i:" << i << "," << fac[i] << endl;

  v[1].parent=&v[0];
  //v[0].ind=0;
  
  ll ans=dfs(&v[1]);
  ans=mod_mul(ans,k);
  
  cout << ans << endl;

  return 0;

}

ll mod_pow(ll x,ll r){
  if(r==0) return 1;
  else if(r==1) return x%mod;
  else if(r%2==0){
    ll t=mod_pow(x,r/2)%mod;
    return t*t %mod;
  } 
  else{
    ll t=mod_pow(x,r/2)%mod;
    ll k= t*t %mod;
    return k*x%mod;
  } 
}
ll mod_add(ll a,ll b){
  return (a+b)%mod;
}

ll mod_mul(ll a,ll b){
  return (a*b)%mod;
}

ll mod_div(ll a,ll b){
  return mod_mul(a,mod_pow(b,mod-2));
}

void make_fact(ll n){
  fac[0]=1;
  rep(i,n){
    fac[i+1]=mod_mul(fac[i],i+1);
  }  
}

void make_invfact(ll n){
  invfac[n]= mod_pow( fac[n] ,mod-2);
  for(int i=n-1;i>=0;i--){
    invfac[i]=mod_mul(invfac[i+1],i+1);
  }

}

Measured memory_bytes: 14720