#include <bits/stdc++.h>

using namespace std;

const int BS = 8000;
const int MAXN = 100005;

int Val[MAXN], B[MAXN], E[MAXN], Sort[MAXN], Dist[MAXN], Size[MAXN];
int now = 0, n;
long long total_paths = 0;

vector<pair<int, int>> G[MAXN];

void dfs(int node) {
	now += 1;
	Val[now] = Dist[node];
	B[node] = now;
	Size[node] = 1;

	for(auto vec : G[node]) {
		if(!B[vec.first]) {
			Dist[vec.first] = Dist[node] + vec.second;
			dfs(vec.first);
			Size[node] += Size[vec.first];
		}
	}

	E[node] = now;
	total_paths += Size[node] - 1;
}

void preprocess() {
	for(int i = 1; i <= now; ++i) {
		Sort[i] = Val[i];
		if(i % BS == 0) {
			sort(Sort + i - BS, Sort + i);
		}
	}
}

int query(int l, int r, int k) {	
	int ans = 0;

	for(int i = l; i <= r;) {
		ans += (Val[i] <= k);
		i += 1;
	}
	return ans;
}

long long solve(int k) {
	long long ans = 0;
	for(int i = 1; i <= n; ++i) {
		if(k + Dist[i] < 0)
			ans += E[i] - B[i];
		else 
			ans += query(B[i] + 1, E[i], k + Dist[i]);
	}
	return ans;
}

int32_t main() {
	int a, b, c;

	long long m;
	cin >> n >> m;
	for(int i = 2; i <= n; ++i) {
		cin >> a >> b >> c;
		G[a].push_back({b, c});
		G[b].push_back({a, c});
	}

	dfs(1);
	preprocess();

	if(m > total_paths) {
		cout << -1;
		return 0;
	}

	int ans = -1;
	for(int step = (1 << 29); step; step >>= 1) {
		if(solve(step + ans) < m)
			ans += step;
	}

	cout << ans + 1;
	return 0;
}