#![allow(unused)] use std::io::{self, BufRead, Write}; pub struct Input { src: R, buf: Vec, pos: usize, } impl Input { pub fn new(src: R) -> Self { Self { src, buf: Vec::new(), pos: 0, } } pub fn input_bytes(&mut self) -> &[u8] { loop { self.advance_until(|b| b.is_ascii_whitespace()); if self.pos == self.buf.len() { self.buf.clear(); self.src .read_until(b'\n', &mut self.buf) .expect("input error"); self.pos = 0; } else { break; } } let l = self.pos; self.advance_until(|b| !b.is_ascii_whitespace()); &self.buf[l..self.pos] } fn advance_until(&mut self, f: impl Fn(u8) -> bool) { while let Some(b) = self.buf.get(self.pos) { if !f(*b) { break; } self.pos += 1; } } pub fn input(&mut self) -> T where ::Err: std::fmt::Debug, { String::from_utf8_lossy(self.input_bytes()) .parse() .expect("parse error") } } pub fn mod_pow(a: i64, b: i64, m: i64) -> i64 { let mut b = b; let mut x = a; let mut y = 1; while b > 0 { if b & 1 == 1 { y = y * x % m; } x = x * x % m; b >>= 1; } y } pub fn mod_inv(x: i64, m: i64) -> i64 { mod_pow(x, m - 2, m) } struct Combination { m: i64, fact: Vec, } impl Combination { pub fn new(size: usize, m: i64) -> Self { let mut comb = Self { m, fact: Vec::new(), }; comb.resize(size); comb } pub fn resize(&mut self, size: usize) { let old_len = self.fact.len(); self.fact.resize(size + 1, 0); for i in old_len..size + 1 { self.fact[i] = if i == 0 { 1 } else { i as i64 * self.fact[i - 1] % self.m }; } } pub fn fact(&self, x: i64) -> i64 { self.fact[x as usize] } pub fn perm(&self, a: i64, b: i64) -> i64 { if a >= b { self.fact(a) * mod_inv(self.fact(a - b), self.m) % self.m } else { 0 } } pub fn comb(&self, a: i64, b: i64) -> i64 { if a >= b { self.fact(a) * mod_inv(self.fact(b) * self.fact(a - b) % self.m, self.m) % self.m } else { 0 } } } fn dfs(u: usize, p: usize, g: &Vec>, depth: &mut [i64]) { for &v in &g[u] { if v == p { continue; } depth[v] = depth[u] + 1; dfs(v, u, g, depth); } } fn main() { let stdin = io::stdin(); let mut input = Input::new(stdin.lock()); let stdout = io::stdout(); let mut out = io::BufWriter::new(stdout.lock()); let stderr = io::stderr(); let mut err = io::BufWriter::new(stderr.lock()); const MOD: i64 = 1e9 as i64 + 7; let n = input.input(); let mut g = vec![Vec::new(); n + 1]; for i in 0..n - 1 { let u: usize = input.input(); let v: usize = input.input(); g[u].push(v); g[v].push(u); } let mut depth = vec![1; n + 1]; dfs(1, 0, &g, &mut depth); let mut exp = 0; for &d in depth.iter().skip(1) { exp += mod_inv(d, MOD); } let comb = Combination::new(n, MOD); let ans = exp % MOD * comb.fact(n as i64) % MOD; writeln!(&mut out, "{}", ans); }