#include <bits/stdc++.h>
#include <atcoder/all>
#define int long long
#define endl "\n"
#define all(n) n.begin(),n.end()
#define rall(n) n.rbegin(),n.rend()
#define rep(i, s, n) for (int i = s; i < (int)(n); i++)
#define floatset(n) fixed<<setprecision(n)
#define rangeout(x,y,h,w) (x<0||y<0||h-1<x||w-1<y)
using namespace std;
using namespace atcoder;
template<class T>using vec=vector<T>;
template<class T>using min_queue=priority_queue<T,vector<T>,greater<T>>;
using ll = long long;
using ld = long double;
using pll = pair<ll,ll>;
using Graph = vector<vector<int>>;
struct Edge1{ll to,cost;};
using WGraph = vec<vec<Edge1>>;
struct BellEdge{ll from,to,cost;};
using BGraph=vec<BellEdge>;
constexpr ll INF = 1e18;
constexpr ll mod = 1000000007;
constexpr ll MOD = 998244353;
constexpr int dx[4]={1,0,-1,0};
constexpr int dy[4]={0,1,0,-1};
template<typename T>
bool chmin(T&a,T b){return a>b?a=b,true:false;}
template<typename T>
bool chmax(T&a,T b){return a<b?a=b,true:false;}
bool Flag(int bit,int i){return (bit&(1LL<<i));}
template<typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val){
    fill( (T*)array, (T*)(array+N), val );
}
template <typename ...Args>
void read(Args &...args) {
   ( std::cin >> ... >> args );
}
int N,K;
vec<int>G[2010];
int sz[2010];
modint1000000007 dp[2010][2010],nxt[2010];
void dfs(int pa,int now){
    sz[now]=1;
    dp[now][1]=1;
    for(auto&x:G[now])if(pa!=x){
        dfs(now,x);
        for(int i=0;i<=sz[now];i++){
            for(int j=0;j<=sz[x];j++){
                nxt[i+j]+=dp[now][i]*dp[x][j];
            }
        }
        sz[now]+=sz[x];
        swap(dp[now],nxt);
        Fill(nxt,0);
    }
    dp[now][0]=1;
}
signed main(){
    read(N,K);
    for(int i=0;i<N-1;i++){
        int A,B;
        cin>>A>>B;
        G[A].push_back(B);
        G[B].push_back(A);
    }
    dfs(-1,0);
    cout<<dp[0][N-K].val()<<endl;
}