pub mod io { use std::io::{BufRead, ErrorKind}; pub fn scan(r: &mut R) -> Vec { let mut res = Vec::new(); loop { let buf = match r.fill_buf() { Ok(buf) => buf, Err(e) if e.kind() == ErrorKind::Interrupted => continue, Err(e) => panic!("{}", e), }; let (done, used, buf) = { match buf.iter().position(u8::is_ascii_whitespace) { Some(i) => (i > 0 || res.len() > 0, i + 1, &buf[..i]), None => (buf.is_empty(), buf.len(), buf), } }; res.extend_from_slice(buf); r.consume(used); if done { return res; } } } #[macro_export] macro_rules! scan { ($r:expr, [$t:tt; $n:expr]) => { (0..$n).map(|_| scan!($r, $t)).collect::>() }; ($r:expr, [$t:tt]) => { scan!($r, [$t; scan!($r, usize)]) }; ($r:expr, ($($t:tt),*)) => { ($(scan!($r, $t)),*) }; ($r:expr, Usize1) => { scan!($r, usize) - 1 }; ($r:expr, Bytes) => { io::scan($r) }; ($r:expr, String) => { String::from_utf8(scan!($r, Bytes)).unwrap() }; ($r:expr, $t:ty) => { scan!($r, String).parse::<$t>().unwrap() }; } #[macro_export] macro_rules! input { ($r:expr, $($($v:ident)* : $t:tt),* $(,)?) => { $(let $($v)* = scan!($r, $t);)* }; } } fn run(reader: &mut R, writer: &mut W) { input! { reader, n: usize, q: usize, ops: [(Usize1, Usize1); q], } let mut lamp = vec![0; n]; let mut count = 0; for (l, r) in ops { for lamp in lamp[l..=r].iter_mut() { if *lamp == 1 { *lamp = 0; count -= 1; } else { *lamp = 1; count += 1; } } writeln!(writer, "{}", count).ok(); } } fn main() { let (stdin, stdout) = (std::io::stdin(), std::io::stdout()); let ref mut reader = std::io::BufReader::new(stdin.lock()); let ref mut writer = std::io::BufWriter::new(stdout.lock()); run(reader, writer); }