//https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 より
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}

// ここまで

fn run() {
    input! {
        n: usize,
        e: [(usize1, usize1, u64); n - 1],
    }
    let mut g = vec![vec![]; n];
    for &(a, b, _) in e.iter() {
        g[a].push(b);
        g[b].push(a);
    }
    let mut used = vec![false; n];
    let mut q = Vec::with_capacity(n);
    let mut s = vec![];
    s.push(0);
    while let Some(v) = s.pop() {
        used[v] = true;
        q.push(v);
        for &u in g[v].iter() {
            if used[u] {
                continue;
            }
            s.push(u);
        }
    }
    let mut size = vec![0; n];
    for &v in q.iter().rev() {
        size[v] = 1;
        for &u in g[v].iter() {
            size[v] += size[u];
        }
    }
    let mut ans = 0;
    for (a, b, c) in e {
        let s = std::cmp::min(size[a], size[b]);
        ans += 2 * (s * (n - s)) as u64 * c;
    }
    println!("{}", ans);
}

fn main() {
    run();
}