#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define sl(n) scanf("%lld", &n)
#define sf(n) scanf("%lf", &n)
#define si(n) scanf("%d", &n)
#define ss(n) scanf("%s", n)
#define pii pair <int, int>
#define pll pair <ll, ll>
#define plp pair <int, pll >
#define pb push_back

#define fr first
#define sc second

vector <ll> ed[300], tree[300];

ll dn[300], rt[300];

void gdfs(ll n, ll par, ll take, ll right)
{
    //  cout << "gdfs " << n << " " << par << " " << take << endl;

    if (take)
        dn[par] = n;

    if (right != -1)
        rt[n] = right;

    ll cn = 0;

    for (ll i = 0; i < ed[n].size(); i++)
    {
        ll v = ed[n][i];

        if (v != par)
            gdfs(v, n, cn==0?1:0, (i<ed[n].size()-1?ed[n][i+1]:-1));

        if (v != par)
            cn++;
    }
}

bool vis[210][210][2][2];

ll dp[210][210][2][2];

ll mod = 1000000007;

ll dfs(ll n, ll rem, ll pok, ll par)
{
    //  cout << n << " beg " << rem << " " << ok << " " << vis[n][rem][ok] << endl;
    if (n == 201)
    {
        if (rem == 0 && pok == 1)
            return 1;
        return 0;
    }

    if (rem == 0)
        return (pok == 1);

    ll &ret = dp[n][rem][pok][par];

    if (vis[n][rem][pok][par])
        return ret;
    vis[n][rem][pok][par] = 1;

    ret = 0;

    ll down = dn[n], right = rt[n], rm;


    if (right != 0)
    {
        rm = rem - 1;

        for (ll i = 0; i <= rm; i++)
        {
            ll x = dfs(down, i, par==1?1:0, 1);
            ll y = dfs(right, rm-i, 1, par);

            ret = (ret + ((x*y)%mod))%mod;
        }

        rm = rem;

        for (ll i = 0; i <= rm; i++)
        {
            ll x = dfs(down, i, 1, 0);
            ll y = dfs(right, rm-i, pok, par);

            ret = (ret + ((x*y)%mod))%mod;
        }
    }
    else
    {
        ret = (ret + dfs(down, rem-1, par==1?1:0, 1))%mod;
        if (pok == 1)
            ret = (ret + dfs(down, rem, 1, 0))%mod;
    }

//    cout << n << " " << rem << " " << pok << " " << par << " " << ret << endl;

    return ret;
}

int main ()
{
    //  freopen("inl.txt", "r", stdin);
    // freopen("outu.txt", "w", stdout);
    //  ios_base::sync_with_stdio(0); // no printf/scanf must be present
    ll cs, t, i, j, k, x, y, z, ans, q, m, n;

    for (cs = 1; sl(n)!=EOF; cs++)
    {
        sl(k);

        for (i = 1; i <= n; i++)
        {
            ed[i].clear();
            tree[i].clear();
            dn[i] = 201;
            rt[i] = 0;
        }

        for (i = 1; i < n; i++)
        {
            sl(x);
            sl(y);

            ed[x].pb(y);
            ed[y].pb(x);
        }

        gdfs(1, 0, 1, -1);

        memset(vis, 0, sizeof(vis));

        printf("%lld\n", dfs(1, k, 1, 0));
    }

    return 0;
}