pub mod io {
    use std::io::{BufRead, ErrorKind};
    use std::str::{self, FromStr};

    pub fn scan<R: BufRead, T: FromStr>(r: &mut R) -> T {
        let mut tmp = 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, mut buf) = {
                match buf.iter().position(u8::is_ascii_whitespace) {
                    Some(i) => (i > 0 || tmp.len() > 0, i + 1, &buf[..i]),
                    None => (buf.is_empty(), buf.len(), buf),
                }
            };
            if done {
                if tmp.len() > 0 {
                    tmp.extend_from_slice(buf);
                    buf = &tmp;
                }
                let res = str::from_utf8(buf).unwrap().parse();
                r.consume(used);
                return res.ok().unwrap();
            }
            tmp.extend_from_slice(buf);
            r.consume(used);
        }
    }

    #[macro_export]
    macro_rules! scan {
        ($r:expr, [$t:tt; $n:expr]) => {
            (0..$n).map(|_| scan!($r, $t)).collect::<Vec<_>>()
        };
        ($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) => {
            scan!($r, String).into_bytes()
        };
        ($r:expr, $t:ty) => {
            io::scan::<_, $t>($r)
        };
    }

    #[macro_export]
    macro_rules! input {
        ($r:expr, $($($v:ident)* : $t:tt),* $(,)?) => {
            $(let $($v)* = scan!($r, $t);)*
        };
    }
}

fn run<R: std::io::BufRead, W: std::io::Write>(reader: &mut R, writer: &mut W) {
    input! {
        reader,
        n: u32, m: usize,
        mut pairs: [(u32, u32); m],
    }
    pairs.sort();

    let mut count = 0;
    let mut right = None;
    for (l, r) in pairs {
        if let Some(i) = right {
            if i < l {
                count += 1;
                right = Some(r);
            } else if r < i {
                right = Some(r);
            }
        } else {
            count += 1;
            right = Some(r);
        }
    }
    writeln!(writer, "{}", n - 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);
}