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));
    }

    fn dfs(graph: &[Vec<(usize, i64)>], u: usize, p: usize, down: i64, ans: &mut i64) -> i64 {
        *ans = down.max(*ans);
        let mut up = 0;
        for &(v, w) in &graph[u] {
            if v == p {
                continue;
            }
            let child_down = down.max(up) + w;
            let child_up = dfs(graph, v, u, child_down, ans);
            up = up.max(child_up + w);
        }
        up
    }

    let mut ans = 0;
    for _ in 0 .. 2 {
        dfs(&graph, 0, 0, 0, &mut ans);
        for v in 0 .. n {
            graph[v].reverse();
        }
    }
    println!("{ans}");
}