n, m = read_line.split.map(&.to_i)
prev = -1
puts n - (1..m).map {
  {Int32, Int32}.from read_line.split.map(&.to_i)
}.sort_by { |l, r| {r, l} }.count { |l, r|
  if l <= prev
    false
  else
    prev = r
    true
  end
}