#![allow(non_snake_case, unused_imports, unused_must_use)] use std::io::{self, prelude::*}; use std::str; fn main() { let (stdin, stdout) = (io::stdin(), io::stdout()); let mut scan = Scanner::new(stdin.lock()); let mut out = io::BufWriter::new(stdout.lock()); macro_rules! input { ($T: ty) => { scan.token::<$T>() }; ($T: ty, $N: expr) => { (0..$N).map(|_| scan.token::<$T>()).collect::>() }; } let N = input!(usize); let mut graph = vec![vec![]; N]; for _ in 0..N - 1 { let (u, v) = (input!(usize) - 1, input!(usize) - 1); graph[u].push(v); graph[v].push(u); } // 距離が低い方にだけ移動するような探索 let mut ans = 0usize; for i in 0..N { let mut q = std::collections::VecDeque::new(); q.push_front(i); let mut seen = std::collections::HashSet::new(); seen.insert(i); let mut dist = std::collections::HashMap::new(); dist.insert(i, 0_usize); while let Some(now) = q.pop_front() { let dnow = *dist.get(&now).unwrap(); if dnow == 3 { continue; } for &nxt in graph[now].iter() { if seen.contains(&nxt) { continue; } q.push_back(nxt); seen.insert(nxt); dist.insert(nxt, dnow + 1); ans += 1; } } } writeln!(out, "{}", ans / 2); } struct Scanner { reader: R, buf_str: Vec, buf_iter: str::SplitWhitespace<'static>, } impl Scanner { fn new(reader: R) -> Self { Self { reader, buf_str: vec![], buf_iter: "".split_whitespace(), } } fn token(&mut self) -> T { loop { if let Some(token) = self.buf_iter.next() { return token.parse().ok().expect("Failed parse"); } self.buf_str.clear(); self.reader .read_until(b'\n', &mut self.buf_str) .expect("Failed read"); self.buf_iter = unsafe { let slice = str::from_utf8_unchecked(&self.buf_str); std::mem::transmute(slice.split_whitespace()) } } } }