#include <bits/stdc++.h>
using namespace std;
#define PB push_back
#define ZERO (1e-10)
#define INF (1<<29)
#define CL(A,I) (memset(A,I,sizeof(A)))
#define DEB printf("DEB!"\n);
#define D(X) cout << "  "<<#X<<": "<<X<<endl;
#define EQ(A,B) (A+ZERO>B&&A-ZERO<B)
typedef long long ll;
typedef long long LINT;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
#define IN(n) int n; scanf("%d", &(n));
#define FOR(i, m, n) for (int i(m); i<n; i++)
#define REP(i, n) FOR(i, 0, n)
#define F(n) REP(i, n)
#define FF(n) REP(j, n)
#define FT(m, n) FOR(k, m, n)
#define aa first
#define bb second
#define FI first
#define SE second
void ga(int N, int *A){F(N)scanf("%d",A+i);}
#define MOD (1000000007)
#define MX (201)
int N,K,a,b;
ll dp[MX][MX][2][2],db[MX][MX][MX][2][2],S[MX][MX];
vi g[MX],w[MX];
ll dyn(int u,int K,bool x,bool y,int p);
ll dyb(int u,int e,int K,bool x,bool y,int p){
    if(e==(int)g[u].size())return (!x||y)&&!K;
    if(g[u][e]==p)return dyb(u,e+1,K,x,y,p);//TODO
    if(S[u][e]<K)return 0;
    ll &v=db[u][e][K][x][y],L=min(w[u][e],K)+1;
    if(~v)return v;
    v=0;
    F(L){
        v+=dyn(g[u][e],i,1,x,u)*dyb(u,e+1,K-i,x,1,p)%MOD;           
        v+=dyn(g[u][e],i,0,x,u)*dyb(u,e+1,K-i,x,y,p)%MOD;
        v%=MOD;
    }
    return v;
}
ll dyn(int u,int K,bool x,bool y,int p){
    if(!K&&x)return 0;
    ll &v=dp[u][K][x][y];
    if(~v)return v;
    return v=dyb(u,0,K-x,x,x&&y,p);
}
int dfs(int u,int p){
    int S=1;
    for(auto&h:g[u])if(h^p)w[u].PB(dfs(h,u)),S+=w[u].back();
                    else w[u].PB(0);
    return S;
}
int main() {
    while(~scanf("%d%d",&N,&K)){
        F(MX)w[i].clear(),g[i].clear();
        F(N-1)scanf("%d%d",&a,&b),g[--a].PB(--b),g[b].PB(a);
        CL(dp,-1),dfs(0,-1);
//        F(N)FF((int)g[i].size())FT(0,(int)w[i][j]+1)REP(l,2)REP(m,2)db[i][j][k][l][m]=-1;
        F(N)FF((int)g[i].size())FT(0,K+1)REP(l,2)REP(m,2)db[i][j][k][l][m]=-1;
        F(N){
            S[i][g[i].size()-1]=w[i].back();
            for(int j=g[i].size()-2;~j;--j)S[i][j]=S[i][j+1]+w[i][j];
        }
        printf("%lld\n",(dyn(0,K,0,0,-1)+dyn(0,K,1,0,-1))%MOD);
    }
    return 0;
}