fn main() {
    let mut nm = String::new();
    std::io::stdin().read_line(&mut nm).ok();
    let nm: Vec<usize> = nm.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let n = nm[0];
    let m = nm[1];
    let mut pairs = (0..m).map(|_| {
            let mut temp = String::new();
            std::io::stdin().read_line(&mut temp).ok();
            let temp: Vec<isize> = temp.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
            (temp[0]-1, temp[1]-1)
        })
        .collect::<Vec<_>>();

    pairs.sort_by_key(|&(_, y)| y);
    let mut cur = -1;
    let mut result = 0usize;
    for &(l, r) in pairs.iter() {
        if cur >= l { continue; }
        result += 1;
        cur = r;
    }
    println!("{}", n-result);
}