Problem:
Diameter of a Tree

Given a tree T with non-negative weight, find the diameter of the tree.

The diameter of a tree is the maximum distance between two nodes in a tree.

Input

n
s1 t1 w1
s2 t2 w2
:
sn-1 tn-1 wn-1

The first line consists of an integer n which represents the number of nodes in the tree. Every node has a unique ID from 0 to n-1 respectively.

In the following n-1 lines, edges of the tree are given.

si and ti represent end-points of the i-th edge (undirected) and wi represents the weight (distance) of the i-th edge.

Output

Print the diameter of the tree in a line.

Constraints

1 ≤ n ≤ 100,000

0 ≤ wi ≤ 1,000

Sample Input 1

4
0 1 2
1 2 1
1 3 3

Sample Output 1

5

Sample Input 2

4
0 1 1
1 2 2
2 3 4

Sample Output 2

7

Solution in C++14 (judge verdict: Accepted)

#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

const long long MAX = 5100000;
const long long INF = 1LL << 60;
const long long mod = 1000000007LL;
//const long long mod = 998244353LL;

using namespace std;
typedef unsigned long long ull;
typedef long long ll;

int n;
vector<vector<pair<int, int>>> g;

pair<int, int> dfs1(ll cur, ll pre) {
	pair<int, int> ret(0, cur);
	for (auto& next : g[cur]) {
		if (next.first == pre) continue;
		auto cost = dfs1(next.first, cur);
		cost.first += next.second;
		if (ret.first < cost.first) ret = cost;
	}
	return ret;
}


int main()
{
	/*
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	*/
	scanf("%d", &n);
	g.resize(n);
	for (ll i = 0; i < n - 1; i++) {
		int s, t, w; scanf("%d %d %d", &s, &t, &w);
		g[s].emplace_back(t, w);
		g[t].emplace_back(s, w);
	}
	printf("%d\n", dfs1(dfs1(0, -1).second, -1).first);
	return 0;
}