// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 macro_rules! input { ($($r:tt)*) => { let stdin = std::io::stdin(); let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock())); let mut next = move || -> String{ bytes.by_ref().map(|r|r.unwrap() as char) .skip_while(|c|c.is_whitespace()) .take_while(|c|!c.is_whitespace()) .collect() }; input_inner!{next, $($r)*} }; } macro_rules! input_inner { ($next:expr) => {}; ($next:expr,) => {}; ($next:expr, $var:ident : $t:tt $($r:tt)*) => { let $var = read_value!($next, $t); input_inner!{$next $($r)*} }; } macro_rules! read_value { ($next:expr, ( $($t:tt),* )) => { ($(read_value!($next, $t)),*) }; ($next:expr, [ $t:tt ; $len:expr ]) => { (0..$len).map(|_| read_value!($next, $t)).collect::>() }; ($next:expr, usize1) => (read_value!($next, usize) - 1); ($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error")); } trait Change { fn chmax(&mut self, x: Self); fn chmin(&mut self, x: Self); } impl Change for T { fn chmax(&mut self, x: T) { if *self < x { *self = x; } } fn chmin(&mut self, x: T) { if *self > x { *self = x; } } } /** * Union-Find tree. * Verified by https://atcoder.jp/contests/pakencamp-2019-day3/submissions/9253305 */ struct UnionFind { disj: Vec, rank: Vec } impl UnionFind { fn new(n: usize) -> Self { let disj = (0..n).collect(); UnionFind { disj: disj, rank: vec![1; n] } } fn root(&mut self, x: usize) -> usize { if x != self.disj[x] { let par = self.disj[x]; let r = self.root(par); self.disj[x] = r; } self.disj[x] } fn unite(&mut self, x: usize, y: usize) { let mut x = self.root(x); let mut y = self.root(y); if x == y { return } if self.rank[x] > self.rank[y] { std::mem::swap(&mut x, &mut y); } self.disj[x] = y; self.rank[y] += self.rank[x]; } #[allow(unused)] fn is_same_set(&mut self, x: usize, y: usize) -> bool { self.root(x) == self.root(y) } #[allow(unused)] fn size(&mut self, x: usize) -> usize { let x = self.root(x); self.rank[x] } } fn main() { input! { n: usize, abc: [(usize1, usize1, String); n * (n - 1) / 2], } let mut used = 0; let mut uf = UnionFind::new(n); for i in 0..n * (n - 1) / 2 { let (a, b, _) = abc[i]; if !uf.is_same_set(a, b) { uf.unite(a, b); used.chmax(i); } } println!("{}", abc[used].2); }