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#include <bits/stdc++.h>
using namespace std;

#define PII pair<int, int>
#define VI vector<int>
#define VPII vector<PII>
#define LL long long
#define LD long double
#define f first
#define s second
#define MP make_pair
#define PB push_back
#define endl '\n'
#define ALL(c) (c).begin(), (c).end()
#define SIZ(c) (int)(c).size()
#define REP(i, n) for (int i = 0; i < (int)(n); i++)
#define FOR(i, b, e) for (int i = (b); i <= (int)(e); i++)
#define FORD(i, b, e) for (int i = (b); i >= (int)(e); i--)
#define ll long long
#define st f
#define nd s
#define pb PB
#define eb emplace_back
#define mp make_pair				
#define siz(c) SIZ(c)
const int inf = 1e9 + 7;
const LL INF = 1e18L + 7;
 
#define sim template<class n
sim, class s> ostream & operator << (ostream &p, pair<n, s> x)
{return p << "<" << x.f << ", " << x.s << ">";}
sim> auto operator << (ostream &p, n y) ->
typename enable_if<!is_same<n, string>::value, decltype(y.begin(), p)>::type
{int o = 0; p << "{"; for (auto c : y) {if (o++) p << ", "; p << c;} return p << "}";}
void dor() {cerr << endl;}
sim, class...s> void dor(n p, s...y) {cerr << p << " "; dor(y...);}
sim, class s> void mini(n &p, s y) {if (p > y) p = y;}
sim, class s> void maxi(n &p, s y) {if (p < y) p = y;}

#ifdef DEB
#define debug(...) dor(__FUNCTION__, ":", __LINE__, ": ", __VA_ARGS__)
#else
#define debug(...)
#endif

#define I(x) #x " = ", (x), " "
#define A(a, i) #a "[" #i " = ", i, "] = ", a[i], " "

#ifndef LOCAL
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;

template <typename T>
using ordered_set =
	tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

#else
#include</Users/dawid/algo/mac/ordered_set>
#endif


const int mod = 1e9+7;
const int N = 25007;

int n, k, cnt;

ll curr;

vector<pair<int, ll> > G[N];

int sub[N];

ordered_set<pair<ll, int> > S[N];

ll off[N];

void prep(int v)
{
	sub[v] = 1;

	for(auto &it:G[v])
	{
		if(sub[it.st])
		{
			swap(it, G[v].back());
			G[v].pop_back();
			break;
		}
	}

	for(auto &it:G[v])
	{
		prep(it.st);
		sub[v] += sub[it.st];

		if(sub[it.st] > sub[G[v][0].st])
			swap(it, G[v][0]);
	}
}

void dfs(int v)
{
	if(G[v].empty())
	{
		S[v].insert(mp(0, v));
		return;
	}

	int u = G[v][0].st;
	ll w = G[v][0].nd;

	dfs(u);

	S[v].swap(S[u]);
	off[v] = off[u];
	off[v] += w;

	ll re = 0;
	ll mx = curr - re;
	cnt += S[v].order_of_key(mp(mx - off[v], inf));
	S[v].insert(mp(re - off[v], v));

	for(int i = 1; i < siz(G[v]); ++i)
	{
		int u = G[v][i].st;
		ll w = G[v][i].nd;

		dfs(u);

		for(auto it:S[u])
		{
			ll re = w + it.st + off[u];
			ll mx = curr - re;
			cnt += S[v].order_of_key(mp(mx - off[v], inf));
		}

		for(auto it:S[u])
		{
			ll re = w + it.st + off[u];
			S[v].insert(mp(re - off[v], it.nd));
		}
	}

	//debug(v, S[v], off[v]);
}

int check(ll k)
{
	for(int i = 1; i <= n; ++i)
	{
		S[i].clear();
		off[i] = 0;
	}

	curr = k;
	cnt = 0;
	dfs(1);
	return cnt;
}

int32_t main()
{ 
	ios_base::sync_with_stdio(0);
	cin.tie(NULL);

	cin >> n >> k;

	for(int i = 1; i < n; ++i)
	{
		int a, b, c;
		cin >> a >> b >> c;

		ll k = 1;

		while(--c)
			k *= n;

		G[a].eb(b, k);
		G[b].eb(a, k);
	}

	prep(1);

	ll l = 0, r = INF;

	while(l<r)
	{
		ll m = (l+r)/2;

		if(check(m) >= k)
			r = m;
		else
			l = m+1;
	}

	//debug(check(875));

	l %= mod;
	l *= n;
	l %= mod;

	cout << l << endl;
}