#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;
using ll = long long;

const ll NEG_INF = -1e18;

struct Edge {
  int to;
  ll cost;
};

int N;
vector<vector<Edge>> tree;
ll answer = NEG_INF;

ll dfs(int node, int parent) {
  ll max1 = 0, max2 = 0;

  for (const auto& edge : tree[node]) {
    if (edge.to == parent) continue;

    ll childLen = dfs(edge.to, node) + edge.cost;

    if (childLen > max1) {
      max2 = max1;
      max1 = childLen;
    } else if (childLen > max2) {
      max2 = childLen;
    }
  }

  // 更新：このノードを通る直径候補
  answer = max(answer, max1 + max2);

  // このノードから上へ渡す最大長
  return max1;
}

int main() {
  cin >> N;
  tree.resize(N);

  for (int i = 0; i < N - 1; ++i) {
    int a, b;
    ll cost;
    cin >> a >> b >> cost;
    --a;
    --b;  // 1-indexed -> 0-indexed
    tree[a].push_back({b, cost});
    tree[b].push_back({a, cost});
  }

  dfs(0, -1);

  cout << answer << endl;

  return 0;
}