use proconio::{input, marker::Usize1};

fn main() {
    input! {
        n: usize,
        edges: [(Usize1, Usize1, i64); n - 1],
    }

    let mut graph = vec![vec![]; n];
    for &(u, v, w) in &edges {
        graph[u].push((v, w));
        graph[v].push((u, w));
    }

    let dist0 = dfs_dist(&graph, 0);
    let leaf1 = (0 .. n).max_by_key(|&v| dist0[v] ).unwrap();
    let dist1 = dfs_dist(&graph, leaf1);
    let diameter = dist1.into_iter().max().unwrap();
    println!("{diameter}");
}

const INF: i64 = 1_000_000_000_000_000_000;

fn dfs_dist(graph: &[Vec<(usize, i64)>], start: usize) -> Vec<i64> {
    let mut dist = vec![INF; graph.len()];
    dist[start] = 0;
    let mut stack = vec![(start, start)];
    while let Some((u, p)) = stack.pop() {
        for &(v, w) in &graph[u] {
            if v == p {
                continue;
            }
            dist[v] = dist[u] + w;
            stack.push((v, u));
        }
    }
    dist
}