type E = (usize, u64); fn dfs(i: usize, p: usize, g: &Vec>, size: &mut Vec, dp: &mut Vec) { size[i] = 1; for &(j, w) in &g[i] { if j == p { continue; } dfs(j, i, g, size, dp); size[i] += size[j]; dp[i] += dp[j] + w * size[j] as u64; } } fn main() { let stdin = std::io::stdin(); let mut rd = ProconReader::new(stdin.lock()); let n: usize = rd.get(); let mut g = vec![vec![]; n]; for _ in 0..(n - 1) { let u: usize = rd.get(); let v: usize = rd.get(); let w: u64 = rd.get(); g[u - 1].push((v - 1, w)); g[v - 1].push((u - 1, w)); } let mut size = vec![0; n]; let mut dp = vec![0; n]; dfs(0, !0, &g, &mut size, &mut dp); let mut ans = vec![0; n]; ans[0] = dp[0]; use std::collections::VecDeque; let mut q = VecDeque::new(); q.push_back((0, !0)); while let Some((i, p)) = q.pop_front() { for &(j, w) in &g[i] { if j == p { continue; } ans[j] = ans[i] - size[j] as u64 * w + (n - size[j]) as u64 * w; q.push_back((j, i)); } } println!("{}", ans.iter().sum::()); } pub struct ProconReader { r: R, line: String, i: usize, } impl ProconReader { pub fn new(reader: R) -> Self { Self { r: reader, line: String::new(), i: 0, } } pub fn get(&mut self) -> T where T: std::str::FromStr, ::Err: std::fmt::Debug, { self.skip_blanks(); assert!(self.i < self.line.len()); assert_ne!(&self.line[self.i..=self.i], " "); let line = &self.line[self.i..]; let end = line.find(' ').unwrap_or_else(|| line.len()); let s = &line[..end]; self.i += end; s.parse() .unwrap_or_else(|_| panic!("parse error `{}`", self.line)) } fn skip_blanks(&mut self) { loop { let start = self.line[self.i..].find(|ch| ch != ' '); match start { Some(j) => { self.i += j; break; } None => { self.line.clear(); self.i = 0; let num_bytes = self.r.read_line(&mut self.line).unwrap(); assert!(num_bytes > 0, "reached EOF :("); self.line = self.line.trim_end_matches(&['\r', '\n'][..]).to_string(); } } } } pub fn get_vec(&mut self, n: usize) -> Vec where T: std::str::FromStr, ::Err: std::fmt::Debug, { (0..n).map(|_| self.get()).collect() } }