#![allow(unused_imports, unused_macros, dead_code)] macro_rules! min { (.. $x:expr) => {{ let mut it = $x.iter(); it.next().map(|z| it.fold(z, |x, y| min!(x, y))) }}; ($x:expr) => ($x); ($x:expr, $($ys:expr),*) => {{ let t = min!($($ys),*); if $x < t { $x } else { t } }} } macro_rules! max { (.. $x:expr) => {{ let mut it = $x.iter(); it.next().map(|z| it.fold(z, |x, y| max!(x, y))) }}; ($x:expr) => ($x); ($x:expr, $($ys:expr),*) => {{ let t = max!($($ys),*); if $x > t { $x } else { t } }} } macro_rules! ewriteln { ($($args:expr),*) => { let _ = writeln!(&mut std::io::stderr(), $($args),*); }; } macro_rules! trace { ($x:expr) => { ewriteln!(">>> {} = {:?}", stringify!($x), $x) }; ($($xs:expr),*) => { trace!(($($xs),*)) } } macro_rules! flush { () => { std::io::stdout().flush().unwrap(); }; } macro_rules! put { (.. $x:expr) => {{ let mut it = $x.iter(); if let Some(x) = it.next() { print!("{}", x); } for x in it { print!(" {}", x); } println!(""); }}; ($x:expr) => { println!("{}", $x) }; ($x:expr, $($xs:expr),*) => { print!("{} ", $x); put!($($xs),*) } } trait Group: std::ops::Add + std::ops::Sub + std::ops::Neg + std::iter::Sum + Clone + Copy { fn zero() -> Self; } impl Group for i32 { fn zero() -> Self { 0 } } impl Group for i64 { fn zero() -> Self { 0 } } impl Group for i128 { fn zero() -> Self { 0 } } impl Group for f32 { fn zero() -> Self { 0.0 } } impl Group for f64 { fn zero() -> Self { 0.0 } } #[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Debug)] enum Hyper { NegInf, Real(X), Inf, } use Hyper::{Inf, NegInf, Real}; impl Hyper { fn unwrap(self) -> X { if let Hyper::Real(x) = self { x } else { panic!() } } } impl std::ops::Add for Hyper { type Output = Self; fn add(self, rhs: Hyper) -> Hyper { match (self, rhs) { (Real(x), Real(y)) => Real(x + y), (Inf, _) => Inf, (_, Inf) => Inf, _ => NegInf, } } } impl std::ops::Sub for Hyper { type Output = Self; fn sub(self, rhs: Hyper) -> Hyper { self + (-rhs) } } impl std::ops::Neg for Hyper { type Output = Self; fn neg(self) -> Hyper { match self { Inf => NegInf, NegInf => Inf, Real(x) => Real(-x), } } } fn wall(d: &mut Vec>>) { let n = d.len(); for k in 0..n { for i in 0..n { for j in 0..n { d[i][j] = min!(d[i][j], d[i][k] + d[k][j]); } } } } fn main() { let mut sc = Scanner::new(); let n: usize = sc.cin(); let m: usize = sc.cin(); let mut d: Vec>> = vec![vec![Inf; n]; n]; for i in 0..n { d[i][i] = Real(0); } for _ in 0..m { let a = sc.cin::() - 1; let b = sc.cin::() - 1; d[a][b] = Real(1); d[b][a] = Real(1); } wall(&mut d); let mut ans = 0; for i in 0..n { for j in 0..i { if d[i][j] == Real(2) { continue; } for k in 0..j { if d[i][k] == Real(2) { continue; } if d[j][k] == Real(2) { continue; } ans += 1; } } } put!(ans); } use std::collections::VecDeque; use std::io::{self, Write}; use std::str::FromStr; struct Scanner { stdin: io::Stdin, buffer: VecDeque, } impl Scanner { fn new() -> Self { Scanner { stdin: io::stdin(), buffer: VecDeque::new(), } } fn cin(&mut self) -> T { while self.buffer.is_empty() { let mut line = String::new(); let _ = self.stdin.read_line(&mut line); for w in line.split_whitespace() { self.buffer.push_back(String::from(w)); } } self.buffer.pop_front().unwrap().parse::().ok().unwrap() } fn chars(&mut self) -> Vec { self.cin::().chars().collect() } fn vec(&mut self, n: usize) -> Vec { (0..n).map(|_| self.cin()).collect() } }