// Source: https://usaco.guide/general/io
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define eb emplace_back // faster than push_back xD
// pbds UwU
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
#define oset tree<ll, null_type,less<ll>, rb_tree_tag,tree_order_statistics_node_update> // use pair for ms
// my io library :D
#define m1(x) template<class T, class... U> void x(T&& a, U&&... b)
#define m2(x) (ll[]){(x forward<U>(b),0)...}
m1(pr){cout << forward<T>(a); m2(cout << " " <<); cout << "\n";}
m1(re){cin >> forward<T>(a); m2(cin >>);}
const ll MOD = 1e9+7;
ll power(ll b, ll e, ll m) {
ll res = 1;
b %= m;
while (e > 0) {
if (e & 1) res = (res * b) % m;
b = (b * b) % m;
e >>= 1;
}
return res;
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
ll n, d; re(n, d);
for (ll i{}; i < n-1; i++){
ll u, v; re(u, v);
}
ll ans = power(2, d+1, MOD);
pr(ans);
}
